TW201932655A - Surface-modified wholly aromatic polyester fiber and manufacturing method thereof - Google Patents

Abstract

The present invention provides a surface-modified wholly aromatic polyester fiber which has excellent fiber strength, while exhibiting excellent interfacial adhesion to a matrix resin. A surface-modified wholly aromatic polyester fiber according to the present invention contains a wholly aromatic polyester polymer. The ratio of the number of oxygen atoms to the number of carbon atoms in the fiber surface is 30-60%. It is preferable that the molar concentration of carboxy groups present in the fiber surface is 5-16%. A surface-modified wholly aromatic polyester fiber according to the present invention is able to be produced by a production method wherein active oxygen species are caused to act on a wholly aromatic polyester fiber that contains a wholly aromatic polyester polymer, so that the ratio of the number of oxygen atoms to the number of carbon atoms in the fiber surface becomes 30-60%.

Description

Surface modified fully aromatic polyester fiber and manufacturing method thereof

The present invention relates to a surface-modified wholly aromatic polyester fiber and a method for manufacturing the same.

A fiber-reinforced resin (FRP) containing reinforcing fibers and a matrix resin is lightweight and has excellent mechanical properties such as specific strength and specific rigidity, and can be preferably used for automobile components, aircraft components, electronic equipment housings, home appliance housings, and sports. Application components, leisure product components, printed circuit boards, circuit boards, multilayer wiring boards, separators, display substrates, and solar cell substrates.

To maintain the mechanical strength of FRP, it is important to strengthen the interface adhesion between the fiber and the matrix resin. For example, in the composite of carbon fiber and epoxy resin, by forming oxygen-containing functional groups such as -OH group and -COOH group on the surface of the carbon fiber in advance, the carbon fiber and the epoxy resin can be chemically bonded to improve the relationship between these. The interface continues. The interface adhesion force at this time tends to depend on the introduction rate (O / C ratio) of the oxygen-containing functional group.

On the other hand, wholly aromatic polyester fibers are being used in FRP by utilizing characteristics such as high tension and low water absorption. However, in the past The fully aromatic polyester fiber has low interface adhesion with the general matrix resin used for FRP, and it is difficult to realize FRP with high mechanical characteristics.

Non-Patent Document 1 discloses a method for modifying the surface of carbon fibers and wholly aromatic polyester fibers by using atmospheric piezoelectric plasma, vacuum plasma, alkali solution, and ozone microbubble. In the method described in Non-Patent Document 1, although the O / C ratio on the surface of the fiber is higher than that before the treatment, its degree is low, and it is difficult to say that the modification effect is sufficient. In addition, the surface of the fiber is rough, and the interface adhesiveness index with the resin, that is, the interface shear stress is slightly increased or decreased relative to that before the treatment. As described above, Non-Patent Document 1 does not obtain fibers having excellent interface adhesion with a matrix resin.

Patent Document 1 discloses a surface modification method in which a liquid crystal polymer film substrate is etched using a mixed solution of an inorganic alkali compound, an aliphatic amine alcohol, and water (requests 1, 4). Patent Document 1 mentions a wholly aromatic polyester as a liquid crystal polymer (claim 3). When this method is applied to a wholly aromatic polyester fiber, the ester bond in the main chain of the wholly aromatic polyester is cleaved by amine alcohol, and the degree of polymerization on the fiber surface is reduced, so the tension of the fiber may be reduced.

Patent Document 2 discloses a surface modification method, which is a surface modification method of a polymer using a supercritical fluid, comprising: adding an organic substance to a predetermined region on the surface of the polymer; and bringing the supercritical fluid into contact The surface of the polymer containing the organic substance is added to penetrate the organic substance to the surface of the polymer (claim 1). Examples of the above-mentioned polymers include fully aromatic polyesters (claim 4). When this method is applied to wholly aromatic polyester fibers, It is not practical to perform the processing under the condition of continuous process and large-scale equipment.

Prior art literature Patent literature

Patent Document 1 Japanese Patent Laid-Open No. 2006-282791

Patent Document 2 Japanese Patent Laid-Open No. 2006-328381

Non-patent literature

Non-Patent Document 1 Aichi Industry Science and Technology Comprehensive Center Research Report 2013, Mikawa Fiber Technology Center

The present invention has been made in view of the foregoing circumstances, and it is an object of the present invention to provide a surface-modified wholly aromatic polyester fiber having excellent fiber strength and excellent interface adhesion with a matrix resin, and a method for producing the same.

The present invention provides the following surface-modified wholly aromatic polyester fibers of [1] to [3] and a method for producing the same.

[1] A surface-modified wholly aromatic polyester fiber comprising a wholly aromatic polyester polymer, and the ratio of the number of oxygen atoms to the number of carbon atoms on the fiber surface is 30 to 60%.

[2] The surface-modified wholly aromatic polyester fiber according to [1], wherein the molar concentration of the carboxyl group existing on the fiber surface is 5 to 16%.

[3] A method for producing a surface-modified wholly aromatic polyester fiber, which uses an active oxygenate to act on a wholly aromatic polyester fiber containing a wholly aromatic polyester polymer, so that the number of oxygen atoms on the surface of the fiber The ratio to the number of carbon atoms is 30 to 60%.

According to the present invention, a surface-modified wholly aromatic polyester fiber having excellent fiber strength and excellent interface adhesion with a matrix resin, and a method for producing the same can be provided.

Forms used to implement the invention

The present invention will be described in detail below.

The surface-modified wholly aromatic polyester fiber of the present invention includes a wholly aromatic polyester polymer, and can be obtained by melt-spinning a liquid crystalline polyester. The liquid crystalline polyester contains repeating structural units derived from an acid such as an aromatic diol, an aromatic dicarboxylic acid, and an aromatic hydroxycarboxylic acid. As long as the effect of the present invention is not impaired, the chemical composition of the constituent units derived from the aromatic diol, the aromatic dicarboxylic acid, and the aromatic hydroxycarboxylic acid is not particularly limited. As long as the effect of the present invention is not impaired, the liquid crystalline polyester may include other constituent units derived from an aromatic diamine, an aromatic hydroxylamine, and an aromatic aminocarboxylic acid. Examples of preferred constituent units are shown below.

(However, X in the formula is selected from the following structures)

(However, m = 0 ~ 2, Y = hydrogen, a substituent selected from halogen atom, alkyl group, aryl group, aralkyl group, alkoxy group, aryloxy group, aralkoxy group)

In the above formula, Y is a hydrogen atom or a substituent of an aromatic ring. When Y is a substituent, the number is within the range of 1 to the maximum number of substituents that can be introduced into the aromatic ring. Examples of the substituent include a halogen atom (for example, a fluorine atom, a chlorine atom, a bromine atom, and an iodine atom), and an alkyl group (for example, a methyl group, an ethyl group, an isopropyl group, and a tertiary butyl group). 4 alkyl, etc.), alkoxy (e.g. methoxy, ethoxy, isopropoxy, n-butoxy, etc.), aryl (e.g. phenyl, naphthyl, etc.), aralkyl (benzene Methyl (also known as phenylmethyl), and phenethyl (also known as phenylethyl), etc.), aryloxy (such as phenoxy, etc.), aralkyloxy (such as benzyloxy, etc.), etc. .

As a more preferable constitutional unit, the constitutional unit shown by following (1-14) and (16-18) is mentioned. In addition, when a plurality of constituent units represented by a single form may be adopted, a plurality of constituent units represented by a single form may be used in combination.

In the above formula, n is an integer of 1 or 2. A plurality of constituent units having different numbers of n represented by the same chemical formula may also be used in combination. Y1 and Y2 are each independently a hydrogen atom or a substituent, and examples of the substituent are the same as those listed for Y. Preferred Y1 and Y2 include a hydrogen atom, a chlorine atom, a bromine atom, and a methyl group.

In the above formula, Z may be selected from the group represented by the following formula;

The liquid crystalline polyester preferably contains a naphthalene skeleton as a structural unit, and more preferably contains both a structural unit (A) derived from hydroxybenzoic acid and a structural unit (B) derived from hydroxynaphthoic acid. For example, as the constituent unit (A), a constituent unit represented by the following formula (A) can be cited; as the constituent unit (B), a constituent unit represented by the following formula (B) can be cited. From the viewpoint of improving melt formability, the ratio of the constituent unit (A) to the constituent unit (B) is preferably 9/1 to 1/1, more preferably 7/1 to 1/1, and particularly preferably 5 / The range is 1 to 1/1. The total amount of the structural unit (A) and the structural unit (B) in the polymer is preferably 65 mol% or more, more preferably 70 mol% or more, and particularly preferably 80 mol% or more. Preferably, the content of the constituent unit (A) in the polymer is 50 to 70 mol%, and the content of the constituent unit (B) in the polymer is 4 to 45 mol%.

The melting point of the liquid crystalline polyester used in the present invention is not particularly limited, but is preferably 250 to 360 ° C, and more preferably 260 to 320 ° C. In addition, the melting point referred to here refers to the main endothermic peak temperature observed and measured in accordance with the JIS K7121 test method using a differential scanning thermal analyzer (DSC; "TA3000" manufactured by METTLER, Inc.). In this method, using the DSC device described above, a 10-20 mg sample is placed in an aluminum pan, and nitrogen gas as a carrier gas is circulated at 100 cc / min. peak.

Depending on the type of polymer, a clear peak may not appear in the 1st run of DSC measurement. At this time, as long as the temperature is raised to a temperature of 50 ° C higher than the expected flow temperature at a temperature of 50 ° C / min, and held at this temperature for 3 minutes to completely melt, it is cooled to -50 ° C / min to 50 ℃, and then the endothermic peak may be measured at a temperature increase rate of 20 ° C / min.

In addition, as long as the effect of the present invention is not impaired, the liquid crystalline polyester may include polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, and polyfluorene. Other thermoplastic polymers such as amines, polyphenylene sulfide, polyether ether ketone, and fluororesins. The liquid crystalline polyester may also contain various additives such as titanium oxide, kaolin, silica, and barium oxide; carbon black; colorants such as dyes and pigments; antioxidants, ultraviolet absorbers, and light stabilizers.

In the surface-modified wholly aromatic polyester fiber of the present invention, the ratio of the number of oxygen atoms to the number of carbon atoms on the fiber surface (hereinafter referred to as the "O / C ratio") is 30 to 60%.

In addition, in this specification, unless specifically stated otherwise, a "main component" is a component of 50 mass% or more.

Since the surface-modified wholly aromatic polyester fiber of the present invention has an appropriate amount of polar functional groups on the surface of the fiber, the interface adhesion with the matrix resin is excellent. In addition, by performing a surface modification treatment under the condition that the O / C ratio becomes 30 to 60%, an appropriate amount of polar functional groups can be introduced without lowering the fiber strength. Therefore, according to the present invention, it is possible to provide a surface-modified wholly aromatic polyester fiber having excellent fiber strength and excellent interface adhesion with a matrix resin.

In the surface-modified wholly aromatic polyester fiber of the present invention, the molar concentration of the carboxyl group existing on the fiber surface is preferably 5 to 16%. The surface-modified wholly aromatic polyester fiber-based fiber in this aspect is excellent in strength and excellent in interface adhesion with the matrix resin.

The O / C ratio and the molar concentration of the carboxyl group can be measured by the method described in [Example] later.

The method for producing the surface-modified wholly aromatic polyester fiber of the present invention is not particularly limited. In one aspect, the fully aromatic polyester before the surface modification including the wholly aromatic polyester polymer is made to act on the active oxygenate so that the O / C ratio of the fiber surface becomes 30 to 60%. Fiber can be used to produce the surface-modified wholly aromatic polyester fiber of the present invention.

The wholly aromatic polyester fiber before the surface modification can be produced by a known method. An example of the manufacturing method is described below.

First, a raw material containing a wholly aromatic polyester polymer and one or more other thermoplastic polymers according to demand is melt-spun by a known method to obtain a spinning precursor. In this step, the shear rate is preferably 103 sec at a spinning temperature which is 10 ° C or more higher than the melting point of the wholly aromatic polyester polymer, within a temperature range in which the wholly aromatic polyester polymer forms molten liquid crystals. Melting spinning is performed under conditions of ^-1 or more and a spinning head stretching of 20 or more. By spinning under the above-mentioned conditions, molecular alignment is performed, and a spinning filament having excellent mechanical properties such as strength can be obtained.

Secondly, in order to improve mechanical properties such as strength, elastic modulus, abrasion resistance, and fatigue resistance, it is preferable to heat-treat the spun yarn. The heat treatment may be performed under tension or without tension. The heat treatment may be performed while stretching the fibers.

The gas environment of the heat treatment is not particularly limited, and may be only an inert gas environment, or it may be started in an inert gas environment and switched to an active gas environment from halfway. The "inert gas environment" as used herein refers to a gas environment in which the concentration of an active gas such as oxygen is 0.1% by volume or less, specifically an inert gas environment such as nitrogen, argon, and helium, or a reduced-pressure gas environment. The "active gas environment" refers to a gas environment in which the concentration of active gas such as oxygen is 1 vol% or more, and preferably an oxygen-containing gas environment in which the oxygen concentration is 10 vol% or more. In terms of cost, the oxygen-containing gas is preferably air. In addition, since a hydrolysis reaction proceeds in the presence of moisture, both the inert gas environment and the active gas environment are set to a dry gas environment.

A well-known method can be applied to the heat treatment method. Examples include a method using a heating medium such as a heating gas, a method using radiant heat from a heating plate, an infrared heater, and the like, a method of contacting a heat roller and a hot plate, and a high frequency Internal heating methods, etc.

The heat treatment temperature is not particularly limited. When the melting point of the wholly aromatic polyester polymer as a raw material before melt spinning is set to Tm, a temperature range of Tm-35 ° C to Tm-2 ° C is preferred. By performing the heat treatment under the temperature condition, a wholly aromatic polyester fiber having high strength and elastic modulus at high temperature can be obtained. In addition, the heat treatment may be performed at a constant temperature, or may be performed with a temperature curve in which the melting point of the blended fiber gradually increases by heating and the temperature is sequentially increased.

The manufactured wholly aromatic polyester fiber can be processed into any shape according to demand.

The wholly aromatic polyester fiber can also be mixed with other resin fibers.

The fully aromatic polyester fiber can also be processed by mechanical crimping or drawing to perform woven or non-woven processing.

It can also be processed into an anisotropic two-dimensional structure, which is obtained by aligning a plurality of wholly aromatic polyester fibers in one direction, and further arranging a plurality of yarns in parallel with respect to the fiber direction in a vertical direction.

The loom can also be used to make the wholly aromatic polyester fibers into a plain weave or twill weave. Further, a three-dimensional structure can be produced by a braiding treatment.

The surface modification treatment is performed on the wholly aromatic polyester fiber before the surface modification manufactured by the well-known method as described above and processed according to demand. In one aspect, the surface of the wholly aromatic polyester fiber before the surface modification is treated with an active oxygenate to perform the surface oxidation treatment, thereby controlling the O / C ratio of the fiber surface.

Reactive Oxygen Species (ROS: reactive oxygen species) based generic term highly reactive oxygen-containing material may include ozone, oxygen plasma, superoxide (O ₂ ^-), hydrogen peroxide (H ₂ O _2), hydroxyl radical (OH), and singlet oxygen ⁽¹ O ₂₎ and the like.

Active oxygenates can be obtained by various methods, for example, they can be obtained by acting an electron beam, ultraviolet (UV), electric field, and heat on an oxygen source in the atmosphere or a reduced-pressure gas environment. The oxygen source is not particularly limited, and in terms of cost, oxygen in the atmosphere is preferred. The gaseous environment that generates active oxygenates may also include inert gases such as nitrogen, argon, and helium.

Electron beam, UV, electric field, and heat can be directly applied to the fiber surface, and active oxygenates generated in other spaces can also be applied to the fiber surface.

When the electron beam, UV, electric field, and heat are directly applied to the fiber surface, it can impart high activity to the fiber surface, effectively generate polar functional groups on the fiber surface, and effectively improve the O / C ratio. The effect is that the higher the energy of electron beam, UV, electric field, and heat, the more effective it is. Among them, it is preferable to use an excimer UV, a high-frequency electric field, and the like to generate ozone, oxygen plasma, and the like. In addition, when UV is used, the emission center wavelength is not particularly limited. From the viewpoint of the efficiency of generating active oxygen species, it is preferably less than 254 nm, more preferably 220 nm or less, particularly preferably 200 nm or less, and most preferably 180 nm or less.

Specifically, for example, excimer ozone treatment is preferred. In this method, it is considered that active oxygenates such as ozone act. In addition, it is considered that excimer light also functions as an active species. Regarding excimer ozone treatment, reference is made to Example 1 described later.

In addition, a high-frequency (RF) oxygen plasma treatment is preferred. In this method, it is thought that active oxygenates such as an oxygen plasma will act. In this method, uniform surface treatment is possible and preferred. Regarding high-frequency (RF) oxygen plasma treatment, reference is made to Example 2 described later.

In addition, an atmospheric piezoelectric plasma (also referred to as an AP plasma) is preferred. This method may be considered superoxide (O ₂ ^-) may act like reactive oxygen-containing material. In this method, even when directly acting on the surface of the fiber, the electron beam does not easily reach the surface of the fiber, and the damage to the fiber is small, which is preferable. Regarding the atmospheric piezoelectric plasma (AP plasma) treatment, reference is made to Example 3 described later.

When electron beam, UV, electric field, and heat are directly applied to the fiber surface and the fiber is extremely degraded, the active oxygenates generated in other spaces are not allowed to act on the fiber so that these are not directly applied to the fiber. The surface is better. At this time, the active oxygenate generated in another space may be supplied to the fiber using a carrier gas as required. The carrier gas is preferably an inert gas such as nitrogen, argon, or helium.

The pressure when reacting the active oxygenate with the wholly aromatic polyester fiber is not particularly limited, but is preferably 0.1 Pa to 0.1 MPa. For inhibiting the inactivation of active species, the higher the degree of vacuum, the better, more preferably 0.1 ~ 100Pa.

The surface modification to a certain degree increases the O / C ratio with the progress of the treatment, but if it reaches a certain level, the O / C ratio tends to decrease due to the reduction of surface functional groups and the progress of carbonization. If the treatment becomes excessive, the surface of the fiber may be roughened. Roughness of the fiber surface is not preferable because it may reduce the strength of the fiber and reduce the adhesive force at the interface with the matrix resin.

The surface modification treatment is performed under the condition that the O / C ratio of the fiber surface becomes 30 to 60%. The surface modification treatment is preferably performed under the condition that the molar concentration of the carboxyl group existing on the fiber surface becomes 5 to 16%. By processing under these conditions, a suitable amount of polar functional groups can be introduced without lowering the fiber strength.

The surface-modified wholly aromatic polyester fiber of the present invention can be used as a reinforcing fiber. The composite material comprising the surface-modified wholly aromatic polyester fiber of the present invention and a matrix resin can be suitably used as a fiber-reinforced resin (FRP) and the like.

FRP can be manufactured by a well-known method.

The first aspect of the manufacturing method of FRP is a method of impregnating a liquid raw material serving as a matrix resin with a surface-modified wholly aromatic polyester fiber, and then curing the liquid raw material.

The second aspect of the FRP manufacturing method is a method of mixing the surface-modified wholly aromatic polyester fiber with a liquid raw material that becomes a matrix resin, and then curing the liquid raw material.

The surface-modified wholly aromatic polyester fiber used in the production of FRP can be used in any form such as a fiber assembly having a plurality of fibers with voids therein and other various fiber processed products.

The matrix resin is not particularly limited, and examples thereof include thermosetting resins such as unsaturated polyesters, epoxy resins, ammonium resins, and phenol resins; thermoplastic resins such as (meth) acrylic resins, and the like.

The liquid material to be the matrix resin and its curing method can be applied by well-known techniques.

When a thermosetting resin is used as the matrix resin, the liquid raw material that becomes the matrix resin is a thermosetting liquid raw material that becomes the matrix resin by thermosetting. As the thermosetting liquid raw material, a known one may be used, and it may include monomers, dimers of a thermosetting resin, or a precursor polymer of a thermosetting resin having a relatively low molecular weight, and the like. The thermosetting liquid material can be cured by thermosetting.

When a thermoplastic resin is used as the matrix resin, examples of the liquid material used as the matrix resin include a heated melt of the thermoplastic resin, a solution in which the thermoplastic resin is dissolved in a solvent, and a dispersion in which the thermoplastic resin is dispersed in a dispersion medium. The heated molten material of a thermoplastic resin can be solidified by cooling. The solution or dispersion of the thermoplastic resin can be cured by removing the solvent or dispersion medium by drying.

As described above, according to the present invention, it is possible to provide a surface-modified wholly aromatic polyester fiber having excellent fiber strength and excellent interface adhesion with a matrix resin, and a method for producing the same.

The surface-modified wholly aromatic polyester fiber of the present invention can be used as a reinforcing fiber.

The fiber-reinforced resin (FRP) containing the surface-modified wholly aromatic polyester fiber and matrix resin of the present invention is lightweight and has excellent mechanical properties such as specific strength and specific rigidity, and can be preferably used in automobile components, aircraft components, and electronics. Equipment housings, home appliance housings, sporting goods components, leisure goods components, printed circuit boards, circuit boards, multilayer wiring boards, separators, display substrates, and solar cell substrates.

[Example]

Hereinafter, examples and comparative examples of the present invention will be described.

[HT-1536 plain weave sample, surface modification treatment, measurement of O / C ratio and functional group amount, measurement of interfacial shear stress]

As a wholly aromatic polyester fiber, "VECTRAN fiber plain weave (HT-1536)" manufactured by Kuraray was prepared and cut into 15 cm squares. This sample was subjected to ultrasonic cleaning in acetone for 30 minutes, and further subjected to ultrasonic cleaning in hexane for 30 minutes. In Comparative Example 1, the washed HT-1536 plain weave sample was directly supplied for evaluation. In Examples 1 to 3 and Comparative Example 2, the washed HT-1536 plain weave sample was subjected to a surface modification treatment for evaluation.

The HT-1536 plain weave fabric samples before and after the surface modification treatment were measured for the O / C ratio of the fiber surface and the amount of functional groups. In addition, the monofilament was drawn from the samples before and after the surface modification treatment, and the interfacial shear stress was measured.

[HT nonwoven fabric sample, surface modification treatment, production of FRP, and measurement of tensile strength]

As a wholly aromatic polyester fiber, a non-woven fabric containing the same fiber as HT-1536 is prepared. Specifically, the HT fiber (15 dtex) manufactured by Kuraray Co., Ltd. was cut to a length of 38 mm, and then crimped. The nonwoven fabric was formed by hydraulic entanglement at a pressure of 15 MPa, and dried at 80 ° C. The basis weight was 89 g / m ² . This non-woven fabric was cut into 20 cm squares. In Comparative Example 1, the obtained HT nonwoven fabric sample was directly supplied for evaluation. In Examples 1 to 3 and Comparative Example 2, the obtained non-woven fabric was subjected to surface modification treatment for evaluation.

The HT nonwoven fabric sample before and after the surface modification treatment is dripped with an epoxy-based hardening solution containing a monomer of a thermosetting epoxy-based resin, and the epoxy-based resin is impregnated under a vacuum of 0.01 MPa or less. After this treatment, it was heated at 80 ° C. for 15 minutes to thermally harden to obtain a fiber-reinforced resin (FRP). The tensile strength of the obtained FRP was measured.

[Assessment items and methods]

The evaluation items and methods are as follows:

(O / C ratio and functional group amount)

By X-ray photoelectron spectroscopy (XPS analysis), the HT-1536 plain weave sample before and after the surface modification treatment was used to obtain the O / C ratio and the amount of functional groups on the fiber surface. The measurement conditions were set as follows.

XPS device: PHI Quantera SXM; X-ray excitation conditions: 100μm-25W-15kV; cathode: Al; measurement range: 1000μm × 1000μm.

The O / C ratio is calculated from the area intensity of the peak derived from C1s which appears from 282 to 298 eV with respect to the area intensity of the peak derived from O1s which appears from 528 to 538 eV.

Among the peaks derived from C1s appearing at 282 to 298 eV, the peak separation based on the bonding species shown below was performed to calculate the functional group amounts of the hydroxyl group and the carboxyl group, respectively.

C-C, C = C: 284.8eV; C-O: 286.4eV; C = O: 287.6eV; O-C = O: 288.6 eV; O-C (= O) -O: 290.3 eV.

(Interfacial Shear Stress)

For the evaluation of the interface adhesion between the wholly aromatic polyester fiber and the matrix resin before and after the surface modification treatment, the interfacial shear stress (IFSS) was measured by a droplet method using a composite interface property evaluation device. As the device, "HM410" manufactured by Toei Industries was used.

An epoxy-based hardening solution containing a monomer of a thermosetting epoxy-based resin was dropped on the monofilament drawn from the HT-1536 plain weave sample before and after the surface modification treatment. This operation was repeated, and the droplets of the epoxy-based hardening liquid were adhered to a plurality of locations of the sample fibers at intervals. After that, the adhered epoxy-based hardening liquid was heated at 80 ° C. for 3 hours in an atmospheric gas environment to thermally harden it to form a plurality of droplets.

Next, the obtained sample is set on a stand of a composite material interface characteristic evaluation device, and the plurality of droplets are sandwiched and fixed by a pair of blades.

Then, the pedestal is moved for a pull test, and the load is detected by a dynamometer.

From the data of the drawing load, the interfacial shear strength (IFSS) was calculated based on the following formula.

τ = F / π‧d‧L

(In the above formula, each symbol indicates the following meanings. Τ: interfacial shear strength; F: drawing load; d: fiber diameter; L: droplet length).

[Tensile strength of FRP]

The tensile fracture strength was measured for an FRP sample (thickness 0.5 mm) cut out with a width of 25 mm. The measurement conditions were set as follows.

Installation: "AUTOGRAPH AG-2000B" manufactured by Shimadzu Corporation, Distance between chucks: 15cm; Stretching speed: 500mm / min.

[Examples 1 to 3, Comparative Examples 1, 2]

The surface modification treatment conditions in each of Examples 1 to 3 and Comparative Examples 1 and 2 are as follows. In addition, in these examples, conditions other than the surface modification treatment conditions are common conditions.

(Example 1)

Surface modification treatment: excimer ozone treatment, device: "MEIRH-M-200-HK-R2" manufactured by MDExcimer; lamp: MEBF-270BHQ (Xe excimer lamp), wavelength 172nm; illumination: 140mW / cm ² ; irradiation Distance: 17mm; Processing voltage: 14.8V; Air flow rate: 1000cc / min; Transport speed: 16.6mm / second; Number of transports: 5 times (treatment condition 1), 25 times (treatment condition 2), 50 times (treatment condition) 3).

(Example 2)

Surface modification treatment: high-frequency (RF) oxygen plasma treatment; device: "Plasma matine V-1000" manufactured by Mec; electrode: a pair of electrodes with a size of 900cm ² with a distance of 13.5cm between the electrodes, placed near one-side electrode Place the sample; gas environment: vacuum 5.0Pa, flow into oxygen at a flow rate of 115cc / min; frequency: 25MHz; processing power: 300W (processing condition 1), 600W (processing condition 2), 900W (processing condition 3); application time :1 minute.

(Example 3)

Surface modification treatment: atmospheric piezoelectric plasma (AP plasma) treatment; device: "APS-70S" manufactured by PSM; gas environment: a mixed gas of nitrogen (flow rate 150L / min) and dry pure air (flow rate 0.5L / min) ; Processing voltage: 11kV; width of the irradiation port in the transport direction: 20mm; distance between the irradiation port and the sample: 2mm; transport speed: 30mm / sec (processing condition 1), 10mm / sec (processing condition 2), 0.167 mm / second (processing condition 3) (Set the transport speed so that the time for the sample to pass directly under the irradiation opening with a width of 2 cm is 0.67 seconds (processing condition 1), 2 seconds (processing condition 2), 2 minutes (processing Condition 3)).

(Comparative example 1)

Surface modification treatment: None.

(Comparative example 2)

Surface modification treatment: UV-ozone treatment; Device: "PL21-200S" made by SEN LIGHTS; lamp: EUV200GS-14 (low-pressure mercury lamp), wavelength 254nm; irradiation distance: 20mm; processing capacity: 15mW / cm ² .

Processing time: 5 minutes (processing condition 1), 10 minutes (processing condition 2), 15 minutes (processing condition 3).

[Evaluation Results]

Table 1 shows the surface modification treatment conditions and evaluation results in each of Examples 1 to 3 and Comparative Examples 1 and 2.

As shown in Table 1, under any of the treatment conditions in Examples 1 to 3, compared with Comparative Example 1 without surface modification treatment, it can be seen that the O / C ratio of the fiber surface is improved, and the O / C of the fiber surface can be obtained. Surface modified fully aromatic polyester fibers with a C ratio of 30 to 60% and a molar concentration of carboxyl groups present on the fiber surface of 5 to 16%. In these examples (some of which were not measured), compared with Comparative Example 1 without surface modification treatment, significant improvement was seen in the evaluation items of the interfacial shear stress of the fiber and the tensile strength of FRP. Thus, in Examples 1 to 3, a surface-modified wholly aromatic polyester fiber having excellent fiber strength and excellent interface adhesion with a matrix resin can be obtained.

In Comparative Example 2, no improvement in O / C ratio on the surface of the fiber was observed compared to Comparative Example 1 without surface modification treatment under any processing conditions.

The present invention is not limited to the above-mentioned embodiments and examples, and the design can be appropriately changed as long as it does not deviate from the meaning of the present invention.

This application claims priority based on Japanese Application Japanese Patent Application No. 2017-250387 filed on December 27, 2017, and incorporates all of its disclosure herein.

Claims (9)

A surface-modified wholly aromatic polyester fiber comprises a wholly aromatic polyester polymer, and the ratio of the number of oxygen atoms to the number of carbon atoms on the fiber surface is 30 to 60%. For example, the surface-modified wholly aromatic polyester fiber of claim 1 has a molar concentration of carboxyl groups existing on the fiber surface of 5 to 16%. The surface-modified wholly aromatic polyester fiber according to claim 1 or 2, wherein the wholly aromatic polyester polymer includes a structural unit represented by the following formula (A) and a structural unit represented by the following formula (B) , The total amount of the constituent unit (A) and the constituent unit (B) in the polymer is 80 mol% or more, and the content of the constituent unit (A) in the polymer is 50 to 70 mol%; A method for producing a surface-modified wholly aromatic polyester fiber, which uses active oxygenates to act on a wholly aromatic polyester fiber containing a wholly aromatic polyester polymer, so that the number of oxygen atoms on the surface of the fiber is relative to carbon The atomic ratio is 30 to 60%. The method for producing a surface-modified wholly aromatic polyester fiber according to claim 4, wherein the wholly aromatic polyester polymer includes a structural unit represented by the following formula (A) and a structure represented by the following formula (B) Unit, the total amount of the constituent unit (A) and the constituent unit (B) in the polymer is 80 mol% or more, and the content of the constituent unit (A) in the polymer is 50 to 70 mol%; The method for manufacturing a surface-modified wholly aromatic polyester fiber according to claim 4 or 5, wherein the oxygen source of the active oxygenate is oxygen in the atmosphere. The method for producing a surface-modified wholly aromatic polyester fiber according to claim 4 or 5, wherein the active oxygen-containing substance causes at least one selected from the group consisting of an electron beam, ultraviolet rays, an electric field, and heat to act on oxygen From the source. The method for manufacturing a surface-modified wholly aromatic polyester fiber according to claim 4 or 5, wherein the active oxygenate is mixed with at least one inert gas selected from the group consisting of nitrogen, argon, and helium . For example, the method for manufacturing a surface-modified wholly aromatic polyester fiber according to claim 4 or 5, wherein the pressure when reacting the active oxygenate with the wholly aromatic polyester fiber is 0.1 Pa to 0.1 MPa.