TWI798323B - Surface-modified wholly aromatic polyester fiber and manufacturing method thereof - Google Patents

Abstract

The invention provides a surface-modified wholly aromatic polyester fiber with excellent fiber strength and excellent interfacial adhesion with matrix resin. The surface-modified wholly aromatic polyester fiber of the present invention comprises a wholly aromatic polyester polymer. The ratio of the number of oxygen atoms on the fiber surface to the number of carbon atoms is 30~60%. The molar concentration of carboxyl groups present on the fiber surface is preferably 5-16%. The surface-modified wholly aromatic polyester fiber of the present invention can make the number of oxygen atoms on the surface of the fiber relative to the carbon atoms The proportion of the number becomes 30~60% of the manufacturing method to manufacture.

Description

Surface-modified wholly aromatic polyester fiber and its manufacturing method

The invention relates to a surface-modified wholly aromatic polyester fiber and a manufacturing method thereof.

Fiber-reinforced resin (FRP) consisting of reinforcing fibers and matrix resin is lightweight and has excellent mechanical properties such as specific strength and specific rigidity, and can be preferably used in automotive components, aircraft components, electronic equipment housings, home appliance housings, sports Product components, leisure product components, printed circuit boards, circuit boards, multilayer wiring boards, separators, substrates for displays, and solar cell substrates.

To maintain the mechanical strength of FRP, it is important to reinforce the interfacial adhesion between the fiber and the matrix resin. For example, in the compounding of carbon fiber and epoxy resin, oxygen-containing functional groups such as -OH group and -COOH group are formed on the surface of carbon fiber in advance, so that carbon fiber and epoxy resin can be chemically bonded, and the relationship between them can be improved. The interface continues. In addition, the interfacial adhesive force at this time tends to depend on the introduction rate (O/C ratio) of the oxygen-containing functional group.

On the other hand, fully aromatic polyester fibers are being considered for use in FRP by taking advantage of properties such as high tension and low water absorption. However, in the past The wholly aromatic polyester fiber has low interfacial adhesion with general-purpose matrix resins used in FRP, and it is difficult to realize FRP with high mechanical properties.

Non-Patent Document 1 discloses a method using atmospheric pressure plasma, vacuum plasma, alkaline solution, and ozone microbubble as a method for modifying the surface of carbon fibers and wholly aromatic polyester fibers. In the method described in Non-Patent Document 1, although the O/C ratio of the fiber surface is improved compared with that before the treatment, but the degree is low, and the modification effect is hardly sufficient. Also, the surface of the fiber was rough, and the index of interfacial adhesion with the resin, that is, the interfacial shear stress, was slightly increased or decreased compared to that before the treatment. Thus, in Non-Patent Document 1, a fiber excellent in interfacial adhesion with a matrix resin has not been obtained.

Patent Document 1 discloses a surface modification method, which uses a mixture of inorganic alkali compounds, aliphatic amine alcohols, and water to etch liquid crystal polymer film substrates (claims 1 and 4). In Patent Document 1, wholly aromatic polyester is mentioned as a liquid crystal polymer (claim 3). When this method is applied to a wholly aromatic polyester fiber, the ester bond of the main chain of the wholly aromatic polyester is cut off by the amino alcohol, and the degree of polymerization on the surface of the fiber is lowered, which may lower the tension of the fiber.

Patent Document 2 discloses a surface modification method, which is a method for modifying the surface of a polymer using a supercritical fluid, which includes: adding an organic substance to a predetermined area on the surface of the polymer; and contacting the supercritical fluid The surface of the polymer to which the above-mentioned organic substance is added to allow the above-mentioned organic substance to penetrate into the surface of the above-mentioned polymer (claim 1). As an example of the above-mentioned polymer, a wholly aromatic polyester (claim 4) is mentioned. When this method is applied to wholly aromatic polyester fibers, due to the It is difficult to process in a continuous process and increase the size of the device, so it is not practical.

prior art literature patent documents

Patent Document 1 Japanese Unexamined Patent Application Publication No. 2006-282791

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

non-patent literature

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

The present invention was made in view of the above circumstances, and aims to provide a surface-modified wholly aromatic polyester fiber having excellent fiber strength and excellent interfacial adhesion with a matrix resin, and a method for producing the same.

The present invention provides the following [1]-[3] surface-modified wholly aromatic polyester fiber and its manufacturing method.

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

[2] The surface-modified wholly aromatic polyester fiber as described in [1], wherein the molar concentration of carboxyl groups present on the surface of the fiber is 5-16%.

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

According to the present invention, a surface-modified wholly aromatic polyester fiber with excellent fiber strength and excellent interfacial adhesion with matrix resin and its manufacturing method can be provided.

form for carrying out the invention

The present invention will be described in detail below.

The surface-modified wholly aromatic polyester fiber of the present invention comprises a wholly aromatic polyester polymer, and can be obtained by melt-spinning liquid crystalline polyester. The liquid crystalline polyester contains repeating structural units derived from acids such as aromatic diols, aromatic dicarboxylic acids, and aromatic hydroxycarboxylic acids. The chemical constitution of the structural unit derived from an aromatic diol, an aromatic dicarboxylic acid, and an aromatic hydroxycarboxylic acid is not specifically limited unless the effect of this invention is impaired. As long as the effects of the present invention are not impaired, the liquid crystalline polyester may contain other structural units derived from aromatic diamine, aromatic hydroxylamine, aromatic aminocarboxylic acid, and the like. Examples of preferable 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 a halogen atom, an alkyl group, an aryl group, an aralkyl group, an alkoxy group, an aryloxy group, and an aralkyloxy 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. As substituents, halogen atoms (such as fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms, etc.), alkyl groups (such as methyl, ethyl, isopropyl, and tertiary butyl groups with 1 to 2 carbon atoms, etc.) 4 alkyl, etc.), alkoxy (such as methoxy, ethoxy, isopropoxy, and n-butoxy, etc.), aryl (such as phenyl, naphthyl, etc.), aralkyl (benzene Methyl (also known as phenylmethyl), and phenylethyl (also known as phenylethyl), etc.), aryloxy (such as phenoxy, etc.), aralkoxy (such as benzyloxy, etc.), etc. .

As a more preferable structural unit, the structural unit shown to following (1-14) and (16-18) is mentioned. In addition, when a structural unit represented by a single formula can take a plurality of structures, a plurality of structural units represented by a single formula can also be used in combination.

In the above formula, n is an integer of 1 or 2. A plurality of structural units having different numbers of n represented by the same chemical formula may 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 mentioned for Y. Preferred examples of Y1 and Y2 include a hydrogen atom, a chlorine atom, a bromine atom, and a methyl group.

In the above formula, Z can be selected from the groups shown in the following formula;

The liquid crystalline polyester preferably includes a naphthalene skeleton as a constituent unit, and more preferably includes both a constituent unit (A) derived from hydroxybenzoic acid and a constituent unit (B) derived from hydroxynaphthoic acid. For example, as a structural unit (A), the structural unit represented by following formula (A) is mentioned; As a structural unit (B), the structural unit represented by following formula (B) is mentioned. 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 5/1. 1~1/1 range. The total amount of the structural unit (A) and the structural unit (B) in the polymer is preferably at least 65 mol%, more preferably at least 70 mol%, and most preferably at least 80 mol%. Preferably, the content of the structural unit (A) in the polymer is 50-70 mol%, and the content of the structural unit (B) in the polymer is 4-45 mol%.

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

Depending on the type of polymer, a clear peak may not appear in the first run (1st run) of DSC measurement. At this time, as long as the temperature is raised to a temperature 50°C higher than the expected flow temperature at a heating rate of 50°C/min, and kept at this temperature for 3 minutes to completely melt, it is cooled to 50°C at a cooling rate of -80°C/min. °C, and then measure the endothermic peak at a heating rate of 20 °C/min.

In addition, the liquid crystalline polyester may also include polyethylene terephthalate, modified polyethylene terephthalate, polyolefin, polycarbonate, polyamide, etc. within the range that does not impair the effect of the present invention. Other thermoplastic polymers such as amine, polyphenylene sulfide, polyether ether ketone, and fluororesin. The liquid crystalline polyester may also contain inorganic substances such as titanium oxide, kaolin, silicon oxide, and barium oxide; carbon black; colorants such as dyes and pigments; various additives such as 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 on the fiber surface to the number of carbon atoms (hereinafter referred to as "O/C ratio" for short) is 30-60%.

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

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, so it has excellent interfacial adhesion with the matrix resin. In addition, by performing surface modification treatment under the condition that the O/C ratio becomes 30-60%, an appropriate amount of polar functional groups can be introduced without reducing 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 interfacial adhesion with a matrix resin.

In the surface-modified wholly aromatic polyester fiber of the present invention, the molar concentration of carboxyl groups existing on the surface of the fiber is preferably 5-16%. The surface-modified wholly aromatic polyester fiber of the above-mentioned aspect is excellent in fiber strength and excellent in interfacial adhesion with the matrix resin, which is preferable.

The O/C ratio and the molar concentration of carboxyl groups can be measured by the method described in the section of [Examples] below.

The method for producing the surface-modified wholly aromatic polyester fiber of the present invention is not particularly limited. In one aspect, the wholly aromatic polyester before surface modification including the wholly aromatic polyester polymer is acted on in such a way that the O/C ratio of the fiber surface becomes 30 to 60% by active oxygen-containing substances The fiber can be used to produce the above-mentioned surface-modified wholly aromatic polyester fiber of the present invention.

The wholly aromatic polyester fiber before surface modification can be manufactured by a well-known method. Hereinafter, an example of a manufacturing method will be described.

First, a raw material comprising a wholly aromatic polyester polymer and one or more other thermoplastic polymers as required is melt-spun by a known method to obtain a spun yarn. In this step, it is preferable to use a shear rate of 103 sec at a spinning temperature that is 10°C higher than the melting point of the wholly aromatic polyester polymer within the temperature range in which the wholly aromatic polyester polymer forms a molten liquid crystal. Melt spinning is carried out under the conditions of ^-1 or more and spinning head draw of 20 or more. By performing spinning under the above-mentioned conditions, molecular alignment proceeds, and a spun yarn having excellent mechanical properties such as strength can be obtained.

Secondly, in order to improve mechanical properties such as strength, elastic modulus, wear resistance, and fatigue resistance, it is preferable to heat-treat the spinning raw yarn. Heat treatment can be performed under tension or without tension. The heat treatment can also be performed while drawing the fiber.

The gas environment of the heat treatment is not particularly limited, and may be only an inert gas environment, or may start under an inert gas environment and switch to an active gas environment midway. The term "inert gas environment" as used herein refers to a gas environment in which the concentration of active gases such as oxygen is 0.1% by volume or less, specifically, an inert gas environment such as nitrogen, argon, and helium, or a decompressed gas environment. "Active gas environment" refers to a gas environment in which the concentration of active gas such as oxygen is 1% by volume or more, preferably an oxygen-containing gas environment with an oxygen concentration of 10% by volume or more. In terms of cost, the oxygen-containing gas is preferably air. In addition, since the hydrolysis reaction proceeds in the presence of moisture, both the inert gas environment and the active gas environment are set as dry gas environments.

As the heat treatment method, well-known methods can be applied, and examples include the method of using a heating medium such as heating gas, the method of using radiant heat from a heating plate and an infrared heater, the method of making it contact with a hot roller and a hot plate, and the use of high frequency, etc. The internal heating method, etc.

The heat treatment temperature is not particularly limited, but when Tm is the melting point of the wholly aromatic polyester polymer as the raw material before melt spinning, it is preferably in the temperature range of Tm-35°C to Tm-2°C. By performing heat treatment under the above temperature conditions, wholly aromatic polyester fibers having high strength and elastic modulus at high temperatures can be obtained. In addition, the heat treatment can be performed at a certain temperature, and can also be performed with a temperature profile in which the melting point of the blended fiber gradually increases by heating and the temperature rises sequentially.

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

Fully aromatic polyester fibers can also be made into a blended state with other resin fibers.

It is also possible to apply mechanical crimping or drawing-cutting to the wholly aromatic polyester fiber for weaving or non-woven processing.

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

It is also possible to use a loom to make wholly aromatic polyester fibers into plain weave or twill weave cloth. A three-dimensional structure can also be made by further braiding treatment.

Surface modification treatment is carried out on the wholly aromatic polyester fiber before surface modification, which is manufactured by the known method and processed according to the requirements. In one aspect, the O/C ratio on the surface of the fiber can be controlled by allowing active oxygen-containing substances to act on the surface of the wholly aromatic polyester fiber before surface modification to perform surface oxidation treatment.

Reactive oxygen species (ROS: reactive oxygen species) is a general term for highly reactive oxygen species, including ozone, oxygen plasma, superoxide (O ₂ ^- ), hydrogen peroxide (H ₂ O ₂ ), Hydroxyl radical (OH), and singlet oxygen ( ¹ O ₂ ), etc.

Active oxygen-containing compounds can be obtained by various methods. For example, they can be obtained by applying electron beams, ultraviolet rays (UV), electric fields, and heat to oxygen sources in the atmosphere or under reduced pressure gas environments. The oxygen source is not particularly limited, but oxygen in the atmosphere is preferable in terms of cost. The gas environment for generating reactive oxygen species may also include inert gases such as nitrogen, argon, and helium.

The electron beam, UV, electric field, and heat can be directly acted on the surface of the fiber, and the active oxygen-containing substances generated in other spaces can also be made to act on the surface of the fiber.

When the electron beam, UV, electric field, and heat directly act on the fiber surface, it can impart high activity to the fiber surface, effectively generate polar functional groups on the fiber surface, and effectively increase the O/C ratio. The effect of this 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 generate ozone, oxygen plasma, and the like using excimer UV, a high-frequency electric field, and the like. In addition, when UV is used, the emission center wavelength is not particularly limited, but from the viewpoint of the generation efficiency of active oxygen species, it is preferably less than 254 nm, more preferably less than 220 nm, particularly preferably less than 200 nm, and most preferably less than 180 nm.

Specifically, for example, excimer ozone treatment is preferable. In this method, active oxygen-containing substances such as ozone are considered to act. In addition, it is considered that excimer light also acts as an active species. For the excimer ozone treatment, refer to Example 1 described later.

In addition, high frequency (RF) oxygen plasma treatment is preferred. In this method, active oxygen-containing substances such as oxygen plasma are considered to act. In this method, a uniform surface treatment is possible and preferred. For high frequency (RF) oxygen plasma treatment, refer to Example 2 described later.

In addition, atmospheric pressure plasma (also known as AP plasma) treatment is preferred. In this method, active oxygen-containing substances such as superoxide (O ₂ ^- ) are considered to act. In this method, even when the electron beam directly acts on the surface of the fiber, it is difficult for the electron beam to reach the surface of the fiber, and the damage to the fiber is less, which is preferable. For atmospheric pressure plasma (AP plasma) treatment, refer to Example 3 described later.

When the fiber is extremely deteriorated due to the direct action of electron beams, UV, electric field, and heat on the surface of the fiber, it is not allowed to directly act on the fiber, but to allow the active oxygen-containing substances generated in other spaces to act on the fiber Surface is better. At this time, the active oxygen-containing species generated in another space may be supplied to the fiber using a carrier gas as needed. As the carrier gas, inert gases such as nitrogen, argon, and helium are preferable.

The pressure when reacting the active oxygen-containing compound 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 vacuum degree, the better, more preferably 0.1-100Pa.

Surface modification to a certain extent is to increase the O/C ratio with the progress of the treatment, but if it reaches a certain extent, the O/C ratio tends to decrease due to the reduction of surface functional groups and the progress of carbonization. Moreover, if the treatment becomes excessive, roughening may occur on the fiber surface. The roughness of the fiber surface may lead to a reduction in fiber strength and a decrease in interfacial adhesion with the matrix resin, which is undesirable.

The surface modification treatment is carried out under the condition that the O/C ratio of the fiber surface becomes 30~60%. The surface modification treatment is preferably carried out under the condition that the molar concentration of carboxyl groups existing on the fiber surface becomes 5 to 16%. By treating under these conditions, it is possible to introduce an appropriate amount of polar functional groups without reducing 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 used as a fiber reinforced resin (FRP) and the like.

FRP can be produced by known methods.

The method for producing FRP according to the first aspect is a method of impregnating a surface-modified wholly aromatic polyester fiber with a liquid raw material to be a matrix resin, and then solidifying the liquid raw material.

The FRP production method of the second aspect is a method of mixing the surface-modified wholly aromatic polyester fiber with a liquid raw material to be a matrix resin, and then solidifying the liquid raw material.

The surface-modified wholly aromatic polyester fiber used in the production of FRP may be in any form, such as a fiber aggregate in which a plurality of fibers are collected with voids inside, or other various fiber processed products.

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

Known techniques can be applied to the liquid raw material used as the matrix resin and its curing method.

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. The thermosetting liquid raw material can use well-known ones, and may include thermosetting resin monomers, dimers, or precursor polymers of relatively low molecular weight thermosetting resins. Thermosetting liquid raw materials can be cured by thermosetting.

When a thermoplastic resin is used as the matrix resin, examples of the liquid raw material for the matrix resin include heated melts of the thermoplastic resin, solutions in which the thermoplastic resin is dissolved in a solvent, and dispersions in which the thermoplastic resin is dispersed in a dispersion medium. The heated melt of thermoplastic resin can be solidified by cooling. A solution or dispersion of a thermoplastic resin can be cured by drying to remove a solvent or a dispersion medium.

As explained above, according to the present invention, there can be provided a surface-modified wholly aromatic polyester fiber having excellent fiber strength and excellent interfacial adhesion with 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) comprising the surface-modified wholly aromatic polyester fiber of the present invention and the matrix resin is lightweight and has excellent mechanical properties such as specific strength and specific rigidity, and can be preferably used in automobile components, aircraft components, electronic components, etc. Equipment casings, home appliance casings, sporting goods components, leisure product components, printed circuit boards, circuit boards, multilayer wiring boards, separators, substrates for displays, and solar cell substrates, etc.

[Example]

Examples and comparative examples of the present invention will be described below.

[HT-1536 plain weave fabric sample, surface modification treatment, O/C ratio and determination of functional groups, determination of interfacial shear stress]

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

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

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

As the wholly aromatic polyester fiber, a nonwoven fabric containing the same fiber as HT-1536 was prepared. Specifically, HT fiber (15dtex) manufactured by KURARAY Co., Ltd. was cut into a length of 38 mm, crimped, and hydroentangled at a pressure of 15 MPa to form a nonwoven fabric, and dried at 80°C. The weight per unit area was 89 g/m ² . Cut this non-woven fabric into 20cm squares. In Comparative Example 1, the obtained HT nonwoven fabric samples were directly evaluated. Examples 1-3 and Comparative Example 2 were evaluated after surface modification treatment was performed on the obtained non-woven fabrics.

The epoxy-based hardening liquid containing the monomer of the thermosetting epoxy-based resin was dripped on the HT nonwoven fabric sample before and after the surface modification treatment, and the epoxy-based resin was impregnated by applying pressure under a vacuum of 0.01 MPa or less. After this treatment, it was heated at 80° C. for 15 minutes to be thermally cured to obtain a fiber-reinforced resin (FRP). Tensile strength was measured for the obtained FRP.

[Assessment items and evaluation methods]

The assessment items and assessment methods are as follows:

(O/C ratio and functional group amount)

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

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

The O/C ratio was calculated from the area intensity of the peak derived from C1s appearing at 282 to 298 eV relative to the area intensity of the peak derived from O1s appearing at 528 to 538 eV.

In addition, among the peaks derived from C1s appearing at 282~298eV, the peak separation according to the bonding species shown below was performed, and the functional group amounts of hydroxyl and carboxyl groups were calculated respectively.

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

(interface 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 the droplet method using the composite material interface characteristic evaluation device. As the device, "HM410" manufactured by Toei Sangyo Co., Ltd. was used.

An epoxy-based hardening liquid containing a monomer of a thermosetting epoxy-based resin was dropped on the monofilament pulled out from the HT-1536 plain weave sample before and after the surface modification treatment. This operation was repeated, and droplets of the epoxy-based curing liquid were attached to a plurality of places of the sample fibers at intervals. Thereafter, the adhering epoxy-based curing liquid was heated at 80° C. for 3 hours in an air atmosphere to thermally harden it to form a plurality of droplets.

Next, the obtained sample was installed on the pedestal of the composite material interface characteristic evaluation device, and the above-mentioned multiple droplets were clamped and fixed by a pair of blades.

Then, move the pedestal to carry out the pull-out test, and use the dynamometer to detect the pull-out load.

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

τ=F/π‧d‧L

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

[Tensile strength of FRP]

Tensile breaking strength was measured about the FRP sample (thickness 0.5mm) cut out by width 25mm. The measurement conditions were set as follows.

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

[Examples 1 to 3, Comparative Examples 1 and 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, the 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; illuminance: 140mW/cm ² ; irradiation Distance: 17mm; Treatment voltage: 14.8V; Air flow rate: 1000cc/min; Transport speed: 16.6mm/second; Transport times: 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 Corporation; electrodes: a pair of electrodes with a size of 900 cm ² , the distance between electrodes is 13.5 cm, placed near the electrodes on one side Place the sample; gas environment: vacuum degree 5.0Pa, flow in 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 pressure plasma (AP plasma) treatment; Device: "APS-70S" manufactured by PSM Corporation; Gas environment: Mixed gas of nitrogen (flow rate 150L/min) and dry pure air (flow rate 0.5L/min) ;Processing voltage: 11kV; Width of the delivery direction of irradiation port: 20mm; Distance between irradiation port and sample: 2mm; Transport speed: 30mm/second (treatment condition 1), 10mm/second (treatment condition 2), 0.167 mm/second (processing condition 3) (set the transport speed, the time for the sample to pass directly under the irradiation port 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" manufactured by SEN LIGHTS; lamp: EUV200GS-14 (low pressure mercury lamp), wavelength 254nm; irradiation distance: 20mm; processing capacity: 15mW/cm ² .

Treatment time: 5 minutes (treatment condition 1), 10 minutes (treatment condition 2), 15 minutes (treatment condition 3).

[Evaluation Results]

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

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

Under any treatment conditions in Comparative Example 2, compared with Comparative Example 1 without surface modification treatment, no increase in the O/C ratio of the fiber surface was observed.

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 gist of the present invention.

This application claims priority based on Japanese application Japanese Patent Application No. 2017-250387 filed on December 27, 2017, and its entire disclosure is incorporated herein.

Claims (9)

A surface-modified wholly aromatic polyester fiber comprising a wholly aromatic polyester polymer derived from aromatic diols and selected from the group consisting of aromatic dicarboxylic acids and aromatic The structural unit of at least one acid in the group of hydroxycarboxylic acids, the ratio of the number of oxygen atoms to the number of carbon atoms on the fiber surface is 30-60%, and the molar concentration of carboxyl groups present on the fiber surface is 5-16%. Such as the surface-modified wholly aromatic polyester fiber of claim 1, wherein the ratio of the number of oxygen atoms on the surface of the fiber to the number of carbon atoms is 44-60%. The surface-modified wholly aromatic polyester fiber according to claim 1 or 2, wherein the wholly aromatic polyester polymer comprises 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 more than 80 mole%, and the content of the constituent unit (A) in the polymer is 50~70 mole%;

A method for producing surface-modified wholly aromatic polyester fibers, comprising: a preparation step of preparing wholly aromatic polyester fibers comprising wholly aromatic polyester polymers comprising aromatic A structural unit of an aromatic diol, and at least one acid selected from the group consisting of an aromatic dicarboxylic acid and an aromatic hydroxycarboxylic acid, and A surface modification treatment step, which is to perform a surface modification treatment in which active oxygen-containing substances act on the wholly aromatic polyester fiber. In the surface modification treatment step, the surface modification treatment is performed so that after the surface modification treatment , the ratio of the number of oxygen atoms on the fiber surface to the number of carbon atoms is 30-60%, and the molar concentration of carboxyl groups present on the fiber surface is 5-16%. The method for producing surface-modified wholly aromatic polyester fiber according to claim 4, wherein the wholly aromatic polyester polymer comprises 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 more than 80 mole%, and the content of the constituent unit (A) in the polymer is 50~70 mole%;

The method for producing surface-modified wholly aromatic polyester fibers according to claim 4 or 5, wherein the oxygen source of the active oxygen-containing compound is oxygen in the atmosphere. The method for producing surface-modified wholly aromatic polyester fibers as claimed in claim 4 or 5, wherein the active oxygen-containing species acts on oxygen by at least one selected from the group consisting of electron beams, ultraviolet rays, electric fields, and heat. source produced. The method for producing surface-modified wholly aromatic polyester fibers according to claim 4 or 5, wherein the active oxygen-containing species is mixed with at least one inert gas selected from the group consisting of nitrogen, argon, and helium . Such as the manufacturer of the surface modified wholly aromatic polyester fiber of claim 4 or 5 method, wherein the pressure when the active oxygen-containing substance is reacted with the wholly aromatic polyester fiber is 0.1Pa~0.1MPa.