JP7411493B2 - Fiber reinforced resin and its manufacturing method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a fiber reinforced resin and a method for producing the same.

There is a technique described in Patent Document 1 as a technique related to a fiber-reinforced resin in which a resin having dynamic covalent bonds is reinforced with fibers. Patent Document 1 describes a structure in which a plurality of fiber-reinforced resins each having a resin containing a dynamic covalent bond as a matrix resin and reinforcing fibers arranged inside the resin are joined, and the fiber-reinforced resins are bonded together. A fiber-reinforced resin composite is described, which is characterized in that the fiber-reinforced resin composites are joined together by sutures.

JP2019-25841A

Upon investigation by the present inventor, it was found that the fiber-reinforced resin described in Patent Document 1 has room for improvement in oil resistance (resistance to oil).
The problem to be solved by the present invention is to provide a fiber-reinforced resin that exhibits good oil resistance and a method for producing the same.

The fiber-reinforced resin of the present invention includes fibers and a resin having dynamic covalent bonds that are configured to have repeating units containing hydroxyl groups and can be reversibly dissociated or bonded by external stimulation, and includes at least a portion of the above-mentioned fibers. Hydrogen atoms constituting hydroxyl groups are substituted with silane groups containing fluorine atoms. Other solutions will be described later in the detailed description.

According to the present invention, a fiber reinforced resin exhibiting good oil resistance and a method for producing the same can be provided.

It is a perspective view of fiber reinforced resin. FIG. 1A is a cross-sectional view taken along line AA in FIG. 1A. FIG. 3 is an enlarged view of the vicinity of the surface of the fiber-reinforced resin. It is a flowchart which shows the manufacturing method of fiber reinforced resin. It is a figure explaining the reaction of a hydroxyl group and a silane compound. It is a figure explaining a stimulus application process.

EMBODIMENT OF THE INVENTION Hereinafter, the form (this embodiment) for implementing this invention is demonstrated. However, the present invention is not limited to the following content or the content shown in the drawings, and can be implemented with arbitrary modifications within a range that does not significantly impair the effects of the present invention. The present invention can be implemented by combining different embodiments. In the following description, the same members in different embodiments will be denoted by the same reference numerals, and overlapping explanations will be omitted.

FIG. 1A is a perspective view of fiber reinforced resin 1. FIG. The fiber-reinforced resin 1 includes fibers 2 and resin 3, and the resin 3 is reinforced by the fibers 2. The fibers 2 shown by broken lines in FIG. 1A are embedded in the resin 3. The fiber-reinforced resin 1 is constructed by impregnating the resin 3 into the fibers 2 which are woven in a plain weave in the form of a mesh.

FIG. 1B is a cross-sectional view taken along line AA in FIG. 1A. Examples of the fibers 2 include inorganic fibers and organic fibers. Examples of inorganic fibers include aramid fibers, glass fibers, asbestos fibers, carbon fibers, silica fibers, silica-alumina fibers, alumina fibers, zirconia fibers, potassium titanate fibers, tyranno fibers, silicon carbide fibers, and metal fibers. Examples of organic fibers include high-strength polyethylene fibers, polyacetal fibers, aliphatic or aromatic polyamide fibers, polyacrylate fibers, fluorine fibers, boron fibers, polyacrylonitrile fibers, aramid fibers, and PBO (poly-p-phenylenebenzobisoxazole). ) fibers, etc. These fibers can be used alone or in combination.

Among these fibers 2, organic fibers are preferred from the viewpoint of mechanical strength, and carbon fibers are particularly preferred. Carbon fibers can be classified into synthetic polymer-derived carbon fibers (polyacrylonitrile-based, polyvinyl alcohol-based, rayon-based carbon fibers, etc.) and mineral-derived carbon fibers (pitch-based carbon fibers, etc.) depending on their raw materials. Among these, carbon fibers derived from synthetic polymers are preferred from the viewpoint of mechanical strength. Moreover, as the fiber 2, aramid fiber and glass fiber are also preferable from the viewpoint of strength.

The fibers 2 are in the form of continuous fibers, long fibers, short fibers, chopped fibers, etc., and are used in the form of unidirectional material, plain weave, nonwoven fabric, etc. It may also be used by directly adding it to the resin 3. In the illustrated example, the fibers 2 are made of long fibers that are woven into a mesh pattern. However, the shape and state of the fibers 2 are not limited to these examples and the illustrated examples.

The resin 3 is composed of repeating units containing hydroxyl groups, and has a dynamic covalent bond that can be reversibly dissociated or bonded by external stimulation. The external stimulus here is, for example, heat or light. A dynamic covalent bond is a covalent bond that can be reversibly dissociated and bonded by external stimulation. In the fiber reinforced resin 1, dynamic covalent bonds are incorporated into the network structure of the resin 3. In the resin 3 having dynamic covalent bonds, the network structure changes due to the dynamic covalent bonds. Changes in the network structure will be described later with reference to FIG.

Examples of dynamic covalent bonds include, but are not limited to, ester bonds, imine bonds, quaternary ammonium salt bonds, oxazoline bonds, spiro-orthoester bonds, borate ester bonds, and disulfide bonds. Among these, the dynamic covalent bond is preferably an ester bond. Since the dynamic covalent bond is an ester bond, the dynamic covalent bond can be easily transesterified with the hydroxyl group in the resin 3. The following formula (1) shows a chemical formula for transesterification, which is one of the dynamic covalent bonds. Note that the chemical formula shown in formula (1) is a part of the structure obtained by transesterification. In addition, in this chemical reaction formula, R, R' and R'' represent arbitrary chemical structures.

The resin 3 has a polymer layer 3a and a fluorine layer 3b. Fluorine layer 3b is formed on the surface of polymer layer 3a. The surface of the polymer layer 3a here is the interface between the polymer layer 3a and the fluorine layer 3b. The polymer layer 3a and the fluorine layer 3b will be explained with reference to FIG. 2.

FIG. 2 is an enlarged view of the vicinity of the surface of the fiber-reinforced resin 1. The polymer layer 3a and the fluorine layer 3b are normally formed integrally as the resin 3, but in this specification, the polymer layer 3a and the fluorine layer 3b are illustrated separately for the sake of explanation. The polymer layer 3a is configured with repeating units 11 containing hydroxyl groups. In the illustrated example, the hydroxyl group contained in the repeating unit 11 is an oxygen atom produced by a bond between the hydroxyl group and the fluorine layer 3b.

At least one of R ₁ and R ₂ contained in the repeating unit 11 contains a dynamic covalent bond (for example, an ester bond) and is an aliphatic or aromatic linear or branched carbon chain. This carbon chain may also contain atoms other than carbon, such as oxygen, for example in epoxy resins. In this case, although it is not strictly a carbon chain, it will be referred to as a carbon chain in this specification for the sake of simplification of explanation. The structure of the repeating units 11 constituting the polymer layer 3a greatly influences the temperature limit of the fiber-reinforced resin. Therefore, its structure can be determined based on the required heat resistance temperature.

The polymeric layer 3a typically includes repeating units 11 containing the above-mentioned dynamic covalent bonds. Among these, the polymer layer 3a is preferably an epoxy resin made by reacting an epoxy compound with an acid anhydride. By using an epoxy resin made by reacting an epoxy compound with an acid anhydride, it is possible to generate an ester bond and a hydroxyl group, which are dynamic covalent bonds. Therefore, in the illustrated example, the resin 3 (particularly the polymer layer 3a) includes an epoxy resin containing dynamic covalent bonds, and the hydroxyl group 12 is bonded to the polymer terminal of the repeating unit 11.

Among epoxy resins, from the viewpoint of mechanical strength, monomers that form ester bonds upon curing or resins having repeating units 11 containing ester bonds as a monomer skeleton are preferred.

The monomer that forms an ester bond during curing is preferably composed of an epoxy compound having a polyfunctional epoxy group and a carboxylic acid anhydride or polyvalent carboxylic acid as a curing agent.

Preferred examples of the epoxy resin include bisphenol A type resins, novolac type resins, alicyclic resins, and glycidylamine resins. Examples of epoxy compounds include bisphenol A diglycidyl ether, bisphenol F diglycidyl ether, bisphenol S diglycidyl ether, resosinol diglycidyl ether, hexahydrobisphenol A diglycidyl ether, polypropylene glycol diglycidyl ether, and neopentyl glycol diglycidyl ether. Glycidyl ether, phthalic acid diglycidyl ester, dimer acid diglycidyl ester, triglycidyl isocyanurate, tetraglycidyl diaminodiphenylmethane, tetraglycidyl metaxylene diamine, cresol novolac polyglycidyl ether, tetrabromo bisphenol A diglycidyl ether, bisphenol hexafluoroacetone di Examples include, but are not limited to, glycidyl ether.

Examples of carboxylic anhydrides or polyhydric carboxylic acids that are curing agents include phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, methyltetrahydrophthalic anhydride, 3-dodecenylsuccinic anhydride, octenylsuccinic anhydride, Methylhexahydrophthalic anhydride, methylnadic anhydride, dodecylsuccinic anhydride, chlorendic anhydride, pyromellitic anhydride, benzophenonetetracarboxylic anhydride, ethylene glycol bis(anhydrotrimate), methylcyclohexenetetracarboxylic acid Anhydride, trimellitic anhydride, polyazelaic anhydride, ethylene glycol bisanhydrotrimellitate, 1,2,3,4-butanetetracarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, polyvalent fatty acid etc., but are not limited to these.

The polymerized layer 3a may contain a catalyst (hereinafter referred to as "dynamic catalyst") that promotes the dissociation and bonding of dynamic covalent bonds after curing. The dynamic catalyst is preferably one that is uniformly dispersed in the liquid composition (described later) of the polymerization layer 3a. For example, in the case of catalysts that promote transesterification reactions, examples of dynamic catalysts include zinc (II) acetate, zinc (II) acetylacetonate, zinc (II) naphthenate, iron (III) acetylacetone, and cobalt acetylacetone (II). , aluminum isopropoxide, titanium isopropoxide, methoxide (triphenylphosphine) copper (I) complex, ethoxide (triphenylphosphine) copper (I) complex, propoxide (triphenylphosphine) copper (I) complex, isopropoxy do(triphenylphosphine)copper(I) complex, methoxidebis(triphenylphosphine)copper(II) complex, ethoxidebis(triphenylphosphine)copper(II) complex, propoxidebis(triphenylphosphine)copper(II) complex, Isopropoxide bis(triphenylphosphine) copper(II) complex, tris(2,4-pentanedionato)cobalt(III), tin(II) diacetate, tin(II) di(2-ethylhexanoate), Examples include, but are not limited to, N,N-dimethyl-4-aminopyridine, diazabicycloundecene, diazabicyclononene, triazabicyclodecene, and triphenylphosphine.

In addition to the above materials, the polymer layer 3a may be a thermoplastic resin into which a crosslinking component having a covalent bond that can be reversibly dissociated and bonded is introduced. Thermoplastic resins into which such a crosslinking component can be introduced include, but are not limited to, polyethylene, polypropylene, polystyrene, polyvinyl chloride, polyethylene terephthalate, acrylic resin, and the like. Further, examples of crosslinking components that can be introduced into the thermoplastic resin include those having an alkoxyamine skeleton, a diarylbibenzofuran skeleton, and a dioxaborane skeleton, but are not limited thereto.

The fluorine layer 3b contains silane groups 13 containing fluorine atoms. The silane group 13 is a functional group represented by -SiR ₃ R ₄ R ₅ . In the illustrated example, R ₅ is an alkyl group in which some hydrogen atoms are substituted with fluorine atoms. At least one of R ₃ , R ₄ , and R ₅ contains a fluorine atom, and each of R 3 , R 4 , and R 5 may be independently substituted with, for example, a hydrogen atom, an alkyl group that may be substituted with a fluorine atom, or a fluorine atom. It is an alkoxy group. The alkyl group may be linear or branched, and may be chain or cyclic.

In the fiber-reinforced resin 1, hydrogen atoms constituting at least some of the hydroxyl groups contained in the repeating units 11 are substituted with silane groups 13. That is, the silicon atom constituting the silane group 13 is bonded to the oxygen atom contained in the repeating unit 11. The oxygen atom to which the silicon atom is bonded is the oxygen atom constituting the hydroxyl group contained in the repeating unit 11. If the silane group 13 is bonded to an oxygen atom at the position of the hydroxyl group in the repeating unit 11, it can be considered that the silane group 13 is bonded to the oxygen atom constituting the hydroxyl group. Whether or not the silane group 13 is bonded to the oxygen atom constituting the hydroxyl group can be determined by identifying the structure of the repeating unit 11 of the polymerized layer 3a, and identifying the position of the hydroxyl group in the repeating unit 11 and the position of the silane group 13. So, you can decide.

In this way, the silane group 13 containing a fluorine atom is bonded to the carbon chain of the repeating unit 11 via the oxygen atom. Therefore, the fluorine layer 3b is chemically bonded to the polymer layer 3a. Therefore, the interfacial adhesion of the fluorine layer 3b to the polymer layer 3a can be increased by chemical bonding.

The silane group 13 has a structure in which a carbon chain composed of a linear or branched alkyl group or a cycloalkyl group is bonded to a silicon atom, and at least a part of the hydrogen atoms contained in the carbon chain are replaced with fluorine atoms. It is preferable that it be substituted with . By using such a silane group 13, oil repellency can be improved and resistance to oil can be improved. Specifically, for example, the silane group 13 includes trifluoropropylsilane, trifluoroethylsilane, etc., but is not limited to these. In the example shown in FIG. 2 above, for silicon constituting the silane group 13, a straight chain alkyl group in which some of the hydrogen atoms are replaced with fluorine atoms, R ₃ which is an alkyl group, and R 3 which is an alkyl group, for example. It is bonded to _R4 .

Note that the number of fluorine atoms is not limited to the illustrated example, and may be one or more. Furthermore, the structure of the carbon chain (carbon chain containing fluorine atoms) bonded to silicon in the fluorine layer 3b is not limited to the illustrated example.

The silane group 13 has a fluorine atom as described above. Therefore, the silane group 13 has a low surface energy, and the silane group 13 is likely to be localized at the air interface, which is the surface. As a result, the oil resistance of the fiber reinforced resin 1 can be improved by the fluorine layer 3b chemically bonded to the polymer layer 3a. Explain about oil resistance

In the fiber reinforced resin 1, an interface exists between the fibers 2 and the resin 3. Therefore, if oil penetrates into the fiber-reinforced resin 1, there is a possibility that the oil may penetrate into the interface between the fibers 2 and the resin 3. Particularly, when the fibers 2 are water-repellent fibers, oil tends to be compatible with the water-repellent fibers, and thus oil tends to enter the interface. Due to the intrusion of oil into the interface, the fibers 2 tend to peel off from the resin 3, and the oil resistance of the fiber reinforced resin 1 decreases.

Therefore, a fluorine layer 3b is placed on the surface of the resin 3. Since the fluorine layer 3b has a low surface energy, the oil repellency on the surface of the resin 3 can be improved. As a result, the intrusion of oil into the resin 3 and the peeling of the fibers 2 from the resin 3 can be suppressed, and the oil resistance of the fiber reinforced resin 1 can be improved.

In the fiber reinforced resin 1, the oil contact angle is, for example, 60° or more, preferably 80° or more. Among these, this range is preferable when the oil is, for example, a lubricating oil and the type of resin 3 is, for example, an epoxy resin. By setting the contact angle within this range, oil penetration can be suppressed and oil resistance can be improved. Note that the contact angle of oil can be measured by using dodecane, which is oil, using a contact angle meter device.

The fiber reinforced resin 1 can be used for any purpose. The fiber-reinforced resin 1 can be used for parts or bodies used in various fields, such as vehicle parts, railway vehicles, ships, aircraft, unit buses, septic tanks, printed circuit boards, play equipment, skis, and the like.

FIG. 3 is a flowchart showing a method for manufacturing the fiber-reinforced resin 1. The method for manufacturing the fiber reinforced resin 1 includes an impregnation step S1 and a curing step S2. It is preferable that the method for manufacturing the fiber reinforced resin 1 further includes a stimulation step S3. The stimulation step S3 may be performed simultaneously with the curing step S2, that is, the curing step S2 may also serve as the stimulation step S3, or the stimulation step S3 may be performed separately after the curing step S2.

In the impregnation step S1, a precursor of the resin 3 (FIG. 1A, FIG. 1B), which is constituted by a repeating unit containing a hydroxyl group and has a dynamic covalent bond that can be reversibly dissociated or bonded by an external stimulus, and fluorine The fiber 2 (FIGS. 1A and 1B) is impregnated with a liquid composition containing a silane compound containing atoms. The resin 3 has the same meaning as the resin 3 described above with reference to FIGS. 1A to 3, and is, for example, an epoxy resin.

The precursor of the resin 3 may be either an uncured raw material composition that forms the resin 3 by curing, or the liquid resin 3 itself. From the viewpoint of easy handling, the precursor of the resin 3 is preferably a raw material composition that forms the resin 3 upon curing. If the resin 3 is, for example, an epoxy resin, the precursor of the resin 3 is, for example, an epoxy compound or a prepolymer. Therefore, for example, the resin 3 including the polymerized layer 3a having hydroxyl groups may be produced by arbitrarily employing the epoxy compound and curing agent mentioned in the description of the polymerized layer 3a above as the raw material composition of the epoxy resin. Note that curing is performed, for example, in a curing step S2 described later.

The hydroxyl group may be present in a raw material that is a precursor (for example, at least one of an epoxy compound or a curing agent), or may be newly generated by a chemical reaction during the reaction (production) of the resin 3. Furthermore, the dynamic covalent bond may be present in the precursor raw material (for example, at least one of the epoxy compound or the curing agent), or may be newly generated by a chemical reaction during the reaction (formation) of the resin 3. good.

A silane compound containing a fluorine atom (hereinafter simply referred to as a silane compound) forms a silane group 13 (FIG. 2) by bonding with a hydroxyl group contained in the polymerized layer 3a (FIG. 2) of the resin 3. The silane compound may be liquid or solid. However, in the case of a solid silane compound, it is preferable that the silane compound is sufficiently dissolved in the liquid composition. The bonding of the silane compound to the hydroxyl group is performed, for example, in the curing step S2 described later.

The silane compound is, for example, an alkoxysilane containing a fluorine atom. The use of such alkoxysilane has the advantage of improving oil resistance due to its low surface energy. Specific examples of the alkoxysilane containing a fluorine atom include trifluoropropyltrimethoxysilane, trifluoroethyltrimethoxysilane, etc., but are not limited thereto.

The content of the silane compound in the liquid composition is preferably 0.1 parts by mass or more and 5 parts by mass or less based on 100 parts by mass of the precursor of resin 3. By setting the content of the silane compound within this range, the fluorine layer 3b can be easily disposed on the surface of the resin 3, and the oil resistance of the resin 3 can be improved.

The liquid composition may also include the dynamic catalyst described with reference to FIG. 2 above.

The fiber 2 is impregnated with a liquid composition containing a precursor of the resin 3 and a silane compound, for example, by placing the plain-woven fiber 2 in a container in a vacuum, and pouring the liquid composition into the container. be able to. However, the specific method of impregnating the fiber 2 is not limited to this.

In the curing step S2, the resin 3 is produced by curing the liquid composition impregnated into the fibers 2 (FIGS. 1A and 1B). When the resin 3 is, for example, an epoxy resin, in the curing step S2, repeating units 11 (FIG. 2) are generated by the reaction between the epoxy compound and the curing agent (acid anhydride, etc.). At the same time, in the curing step S2, the silane compound is bonded to at least one of the hydroxyl groups generated by the reaction or the hydroxyl groups contained in the raw material composition. The hydroxyl group referred to here is the hydroxyl group contained in the repeating unit 11 in the polymer layer 3a (FIG. 2). The bonding of the silane compound to the hydroxyl group will be explained with reference to FIG. 4.

FIG. 4 is a diagram illustrating the reaction between a hydroxyl group and a silane compound. The content of FIG. 4 is an example of a specific form of bonding of a silane compound to a hydroxyl group, and the bonding of a silane compound to a hydroxyl group is not limited to that shown in FIG. 4. In the curing step S2, the silane compound 14 (alkoxysilane in the illustrated example) is hydrolyzed. Then, the hydrolyzed silane compound 14 reacts with the hydroxyl group contained in the polymerized layer 3a, and the silicon atom of the silane compound 14 bonds to the oxygen atom constituting the hydroxyl group. Thereby, as explained with reference to FIG. 2, the silane group 13 is bonded to the repeating unit 11 constituting the polymerized layer 3a via an oxygen atom.

The curing conditions in the curing step S2 are not particularly limited, and may be appropriately determined depending on the specific types and amounts of the resin 3 and the silane compound. When the resin 3 is an epoxy resin and the silane compound is, for example, an alkoxysilane, the liquid composition can be cured, for example, by heating. The heating temperature can be, for example, 40°C or higher and 80°C or lower. The heating time can be, for example, 30 minutes or more and 5 hours or less.

Returning to FIG. 3, in the curing step S2, as described above, the silane groups 13 are bonded to the repeating units 11 constituting the polymerized layer 3a via oxygen atoms. Therefore, most of the silane groups 13 generated by polymerization are taken into the polymer layer 3a, and the silane groups 13 are present inside the polymer layer 3a. Therefore, it is preferable to perform a stimulation step S3 in which the silane groups 13 present inside the polymer layer 3a are exposed to the outside of the polymer layer 3a, that is, to the surface of the resin 3.

In the stimulation step S3, an external stimulation is applied to the dynamic covalent bonds in the resin 3. The resin 3 to which external stimulation is applied may be after curing, may be in the process of being cured, or may be uncured. When the stimulation step S3 also serves as the above-mentioned curing step S2, the heating in the curing step S2 serves as an external stimulus, and the external stimulation is applied to the dynamic covalent bond that originally existed or was newly generated. Application of an external stimulus to the dynamic covalent bond can be performed, for example, by applying an external stimulus to the resin 3.

External stimuli include heat, light, etc., for example. Through the stimulation step S3, the dynamic covalent bonds incorporated in the polymer layer 3a are dissociated and bonded, and the network structure of the polymer layer 3a changes. This increases the number of silane groups 13 exposed on the surface. Changes in the network structure will be explained with reference to FIG. 5.

FIG. 5 is a diagram illustrating the stimulation application step S3. As an example, a case will be described in which the stimulation step S3 is performed after the curing step S2, but when the curing step S2 also serves as the stimulation step S3, the following effects occur in the curing step S2. That is, as the resin 3 hardens, the silane groups 13 are exposed on the surface of the polymerized layer 3a.

At the end of the curing step S2, silane groups 13 are present both on the outside (on the surface of the resin 3) and inside the polymerized layer 3a (left diagram in FIG. 5). If an external stimulus is applied to the resin 3 in this state, the network structure of the polymer layer 3a changes as described above. In addition, when the above-mentioned liquid composition contains a dynamic catalyst, the polymerization layer 3a also contains a dynamic catalyst, and the change in the network structure is promoted. Due to the change in the network structure, the silane groups 13 containing fluorine, which have small energy and a large atomic radius, are exposed to the air interface, which is the surface of the polymer layer 3a. As a result, the silane groups 13 are exposed to the surface of the resin 3, so that the silane groups 13 are localized on the surface (center view in FIG. 5), and the oil resistance of the resin 3 due to the fluorine layer 3b is improved.

After the internal silane groups 13 are exposed to the surface in the stimulation step S3, when external stimulation is further applied, the network structure of the polymerized layer 3a changes again (see the right diagram in FIG. 5). However, there are many hydroxyl groups inside the polymerized layer 3a, and the hydroxyl groups and fluorine atoms do not mix well with each other. Therefore, even if the network structure of the polymer layer 3a changes again, the silane groups 13 present on the surface are difficult to return to the inside of the polymer layer 3a. Therefore, even if the network structure of the polymer layer 3a changes due to external stimulation, the oil resistance of the resin 3 is maintained.

According to the method for manufacturing fiber-reinforced resin 1 shown in FIG. 3, fiber-reinforced resin 1 that exhibits good oil resistance can be manufactured.

Hereinafter, the present invention will be explained in more detail with reference to Examples.

<Example 1>
For 100 parts by mass of epoxy resin (JER828, manufactured by Mitsubishi Chemical Co., Ltd., prepolymer), 47 parts by mass of curing agent (MHAC-P, manufactured by Hitachi Chemical Co., Ltd.), zinc (II) acetylacetonate (manufactured by Tokyo Kasei Co., Ltd., dynamic catalyst). By adding 14 parts by mass and 1 part by mass of trifluoropropyltrimethoxysilane (KBM-7103 manufactured by Shin-Etsu Chemical Co., Ltd., a silane compound, an alkoxysilane containing a fluorine atom), and stirring and mixing in the atmosphere, the liquid composition was prepared. Prepared. The prepared liquid composition was impregnated in a vacuum into a plain-woven sheet of carbon fibers (CO6343 manufactured by Toray Industries, Inc. Fiber 2) (impregnation step S1). Impregnation was performed on the entire eight stacked sheets. After impregnation, it was heated at 60° C. for 2 hours (curing step S2). The generated dynamic covalent bond is an ester bond. After heating, it was cooled and heated again at 180° C. for 2 hours (stimulation step S3). Through the above operations, a fiber reinforced resin 1 having a fluorine layer 3b on the surface of the polymerized layer 3a was produced.

As an evaluation of oil resistance, first, the bending strength before oil impregnation was evaluated in accordance with JIS K7074 "Bending test method for carbon fiber reinforced plastics". Bending strength was evaluated using a bending tester. The test piece used in the bending test had a length of 100 mm and a width of 15 mm, the distance between fulcrums was 80 mm, the test speed was 5 mm/min, the center diameter of the fulcrum was 5 mm, and both ends of the span were 2 mm. The test was conducted at room temperature. A bending test was conducted on each of the five fiber reinforced resins 1 produced by the same method, and the average value of the test results was taken as the bending strength.

Next, the fiber reinforced resin 1 whose bending strength was evaluated was impregnated with lubricating oil at 50° C. for 1000 hours. After 1000 hours had passed, the oil was wiped off and the bending strength was evaluated again using the same method. The bending strength before impregnation and the bending strength after impregnation were compared, and the residual bending strength was calculated by dividing the bending strength after impregnation by the bending strength before impregnation. If the residual bending strength was 80% or more, it was judged that the oil resistance was improved.

As a result of the evaluation, the bending strength before impregnation was 650 MPa, and the bending strength after impregnation was 640 MPa. Therefore, the residual bending strength was 98%, and the oil resistance was good.

<Example 2>
Fiber-reinforced resin 1 was produced in the same manner as in Example 1 except that the amount of trifluoropropyltrimethoxysilane used was changed to 2.5 parts by mass, and the bending strength was evaluated. As a result of the evaluation, the bending strength before impregnation was 644 MPa, and the bending strength after impregnation was 633 MPa. Therefore, the residual bending strength was 98%, and the oil resistance was good.

<Example 3>
Fiber-reinforced resin 1 was produced in the same manner as in Example 1 except that the amount of trifluoropropyltrimethoxysilane used was changed to 5 parts by mass, and the bending strength was evaluated. As a result of the evaluation, the bending strength before impregnation was 637 MPa, and the bending strength after impregnation was 620 MPa. Therefore, the residual bending strength was 97%, and the oil resistance was good.

<Example 4>
Fiber-reinforced resin 1 was produced in the same manner as in Example 1 except that the amount of trifluoropropyltrimethoxysilane used was changed to 0.5 parts by mass, and the bending strength was evaluated. As a result of the evaluation, the bending strength before impregnation was 653 MPa, and the bending strength after impregnation was 637 MPa. Therefore, the residual bending strength was 98%, and the oil resistance was good.

<Example 5>
Fiber-reinforced resin 1 was produced in the same manner as in Example 1 except that the amount of trifluoropropyltrimethoxysilane used was changed to 0.1 part by mass, and the bending strength was evaluated. As a result of the evaluation, the bending strength before impregnation was 662 MPa, and the bending strength after impregnation was 639 MPa. Therefore, the residual bending strength was 97%, and the oil resistance was good.

<Example 6>
Fiber-reinforced resin 1 was produced in the same manner as in Example 1 except that the amount of trifluoropropyltrimethoxysilane used was changed to 0.01 part by mass, and the bending strength was evaluated. As a result of the evaluation, the bending strength before impregnation was 657 MPa, and the bending strength after impregnation was 543 MPa. Therefore, the residual bending strength was 83%, and the oil resistance was good.

<Example 7>
Fiber-reinforced resin 1 was produced in the same manner as in Example 1 except that the amount of trifluoropropyltrimethoxysilane used was changed to 7.5 parts by mass, and the bending strength was evaluated. As a result of the evaluation, the bending strength before impregnation was 622 MPa, and the bending strength after impregnation was 521 MPa. Therefore, the residual bending strength was 84%, and the oil resistance was good.

<Comparative example 1>
A fiber reinforced resin was produced in the same manner as in Example 1 except that trifluoropropyltrimethoxysilane was not used. The fiber-reinforced resin of Comparative Example 1 corresponds to the fiber-reinforced resin described in Patent Document 1 above. Since trifluoropropyltrimethoxysilane is not used, the produced resin does not have the fluorine layer 3b of the fiber reinforced resin 1. The bending strength of the produced fiber-reinforced resin was evaluated. As a result of the evaluation, the bending strength before impregnation was 664 MPa, and the bending strength after impregnation was 474 MPa. Therefore, the residual bending strength was 71%, indicating that the bending strength had decreased due to oil.

<Consideration>
In Examples 1 to 7 regarding the fiber reinforced resin 1 provided with the fluorine layer 3b, the residual bending soil was 80% or more in all cases. For this reason, it was found that even when impregnated with oil at 50° C. for 1000 hours, the bending strength was not significantly affected and the material had excellent oil resistance. In particular, in Examples 1 to 5 in which the amount of the silane compound used was 0.1 parts by mass or more and 5 parts by mass or less, the residual bending strength exceeded 90%. This is thought to be due to the fact that the excess silane group 13 was suppressed from returning to the inside in the stimulation step S3 (FIG. 3), as well as being used in an amount sufficient to form the fluorine layer 3b. . Therefore, it has been found that the amount of the silane compound used in the liquid composition is preferably 0.1 parts by mass or more and 5 parts by mass or less based on 100 parts by mass of the epoxy resin.

On the other hand, in Comparative Example 1 without the fluorine layer 3b, a decrease in residual bending strength was observed. This is considered to be because oil penetrated into the interface between the fiber 2 and the resin 3 during impregnation at 50° C. for 1000 hours, making it easier to peel off. In particular, fibers such as carbon fibers have low surface energy and high affinity for oil. For this reason, the oil that is easily compatible with the fibers 2 is particularly likely to seep into the interface between the fibers 2 and the resin 3 described with reference to FIG. 1B, for example. As a result, it is considered that peeling between the fibers 2 and the resin 3 is likely to occur, and the residual bending strength is reduced.

1 Fiber reinforced resin 2 Fiber 3 Resin 3a Polymer layer 3b Fluorine layer 11 Repeating unit 12 Epoxy group 13 Silane group 14 Silane compound S1 Impregnation step S2 Curing step S3 Stimulation imparting step

Claims (10)

fiber and
A resin configured with a repeating unit containing a hydroxyl group and having a dynamic covalent bond that can be reversibly dissociated or bonded by external stimulation,
A fiber-reinforced resin in which at least some of the hydrogen atoms constituting the hydroxyl groups are substituted with silane groups containing fluorine atoms. The silane group has a structure in which a carbon chain composed of a linear or branched alkyl group or a cycloalkyl group is bonded to a silicon atom, and at least a portion of the hydrogen atoms contained in the carbon chain are replaced by fluorine atoms. The fiber-reinforced resin according to claim 1, wherein the fiber-reinforced resin is substituted with. The fiber reinforced resin according to claim 1 or 2, wherein the fiber is at least one of aramid fiber, glass fiber, and carbon fiber. The fiber reinforced resin according to claim 1 or 2, wherein the dynamic covalent bond is an ester bond. The fiber reinforced resin according to claim 1 or 2, wherein the resin includes an epoxy resin containing the dynamic covalent bond. The fiber reinforced resin according to claim 1 or 2, wherein the contact angle of dodecane, which is oil, is 60° or more. A liquid composition containing a resin precursor having a dynamic covalent bond that is composed of repeating units containing a hydroxyl group and that can be reversibly dissociated or bonded by external stimulation, and a silane compound containing a fluorine atom is used as a fiber. an impregnation step of impregnating the
A method for producing a fiber-reinforced resin, comprising a curing step of producing the resin by curing the liquid composition impregnated into the fibers. The method for producing a fiber-reinforced resin according to claim 7, comprising a stimulation step of applying an external stimulation to the dynamic covalent bonds in the resin. The method for producing a fiber reinforced resin according to claim 7 or 8, wherein the silane compound is an alkoxysilane containing a fluorine atom. The method for producing a fiber reinforced resin according to claim 7 or 8, wherein the content of the silane compound in the liquid composition is 0.1 parts by mass or more and 5 parts by mass or less based on 100 parts by mass of the precursor.

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