JP2023033242A - Sizing agent for carbon fibers - Google Patents

Abstract

To provide a sizing agent for carbon fibers.SOLUTION: A sizing agent for carbon fibers includes, relative to 100 pts.wt. of the total weight of the sizing agent, 2 to 30 pts.wt. of a resin main agent (A) having at least one epoxy compound, 2 to 30 pts.wt. of a resin main agent (B) having at least one acrylate compound, 0.5 to 15 pts.wt. of a surfactant (C), 0.01 to 0.5 pt.wt. of a hindered phenol agent (D), and the balance of a solvent, in which the particle diameter of the sizing agent is in a range from 0.01 to 0.5 μm.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present disclosure relates to a sizing agent for carbon fibers, and more particularly to a sizing agent capable of increasing the curing time of carbon fiber bundles.

Carbon fiber is an important reinforcing material and is widely applied in various fields. Carbon fiber has advantages such as high specific strength and specific modulus, high temperature resistance, chemical resistance, small coefficient of friction, and good electrical conductivity, so it can be used to reinforce material properties. Carbon fiber composite materials can be applied in various fields, such as aviation, space, sporting goods, civil engineering, electronic products, and medical equipment.

However, the processability of carbon fibers can be affected due to the low stretchability and brittleness of carbon fibers. During the carbon fiber processing process, mechanical friction may cause fuzz and thread breakage, which may reduce the strength of the carbon fiber. In addition, the hardness of carbon fibers is one of the factors that affect the occurrence of fluff and yarn breakage due to mechanical friction during processing. The higher the hardness of the carbon fiber, the more likely it is to fluff or break during processing.

In view of the above, there is now an urgent need to develop methods for increasing the processability of carbon fibers so as to overcome the above problems.
The present disclosure has been made in view of the above, and an object thereof is to provide a carbon fiber sizing agent that increases the processability of carbon fibers.

The sizing agent for carbon fiber of the present disclosure comprises a resin main agent (A) comprising 2 to 30 parts by weight of at least one epoxy group compound and 2 to 30 parts by weight of at least A resin main agent (B) consisting of one acrylate compound, 0.5 to 15 parts by weight of a surfactant (C), 0.01 to 0.5 parts by weight of a hindered phenolic reagent (D), and the balance and a solvent, and the particle size of the sizing agent is 0.01 to 0.5 μm.

In some embodiments, the resin base (A) comprising at least one epoxy group compound comprises a bisphenol A type epoxy compound, a bisphenol F type epoxy compound, a bisphenol S type epoxy compound, a phenolic epoxy resin, or a combination thereof. .

In some embodiments, the resin base (A), which consists of at least one epoxy group compound, accounts for 10 to 25 parts by weight.

In some embodiments, the resin main component (B) comprising at least one acrylate compound is an acrylate having an intramolecular oxyalkylene group, a methacrylate having an intramolecular oxyalkylene group, or an intramolecular oxyalkyl group. , methacrylates having an oxyalkyl group in the molecule, acrylates having no oxyalkylene group in the molecule, methacrylates having no oxyalkylene group in the molecule, acrylates having no oxyalkyl group in the molecule, oxyalkyl groups in the molecule or combinations thereof.

In some embodiments, the resin base (B), which consists of at least one acrylate compound, comprises 10 to 25 parts by weight.

In some embodiments, surfactant (C) comprises nonionic surfactants, anionic surfactants, cationic surfactants, or combinations thereof.

In some embodiments, surfactant (C) comprises 5 to 12.5 parts by weight.

In some embodiments, the hindered phenolic reagent (D) comprises 0.05-0.1 parts by weight.

The carbon fiber coated with the carbon fiber sizing agent of the present disclosure has a sizing rate of 0.1 to 5% by weight.

The carbon fiber coated with the carbon fiber sizing agent of the present disclosure exhibits a hardness increase of less than 100% after 14 days of aging is detected.

Hereinafter, the above description will be described in detail with embodiments, and further interpretation of the technical solution of the present disclosure will be made.

The detailed description of the present disclosure can be best understood in conjunction with the accompanying drawings. It should be noted that, according to industry standard specifications, the various features are not drawn to scale and are for illustration purposes only. In practice, the sizes of the various features may be arbitrarily increased or decreased for clarity of illustration.
FIG. 3 illustrates an apparatus for detecting carbon fiber fuzz according to some embodiments of the present disclosure; FIG. 10 illustrates an apparatus for detecting hardness of carbon fibers according to some embodiments of the present disclosure; FIG. 10 illustrates an apparatus for detecting hardness of carbon fibers according to some embodiments of the present disclosure;

As used herein, ranges expressed as "one numerical value to another numerical value" are schematic representations to avoid listing each and every numerical value within the range in the specification. Accordingly, the recitation of any particular numerical range includes any numerical value within that numerical range and any smaller numerical range defined by any numerical value within that numerical range, and any numerical value and any smaller numerical range within that numerical range. It is the same as explicitly described in the specification.

As used herein, "about," "similar," "essentially," or "substantially" take into account the measurements being discussed and the specific number of errors associated with the measurements (i.e., limitations of the measurement system). , mean values within acceptable deviations of said values and specific values as determined by those skilled in the art. For example, "about" can mean within one or more standard deviations, or within ±30%, ±20%, ±15%, ±10%, ±5% of said value. Also, as used herein, "about," "similar," "essentially," or "substantially" does not apply to all properties with one standard deviation, Or depending on other properties, a relatively acceptable deviation range or standard deviation may be selected.

In order to allow the carbon fiber to exhibit its inherent good performance and to avoid degrading the processability of the carbon fiber, a sizing agent is applied to the carbon fiber to make the carbon fiber It is possible to reduce the occurrence of fluff and yarn breakage due to mechanical friction during the processing process of , and to have good workability. Treatment with a sizing agent can improve the workability and workability of the carbon fiber and the bonding strength with the matrix resin, and can impart excellent mechanical properties to the carbon fiber composite material.

Sizing agents can mainly improve the following functions. (1) The carbon fibers can be bundled and wound into a roll, are easy to store and transport, and the carbon fibers can be aligned and used for manipulation during the manufacturing process of the composite material. (2) It protects the carbon fiber and reduces fluff and thread breakage caused by mechanical friction during processing of the carbon fiber. (3) As an interfacial coupling agent between carbon fiber and resin, it improves the problem of poor impregnation of carbon fiber and resin.

In general, the main component of the sizing agent is epoxy resin, which itself has good film-forming properties, forms a strong thin film on the surface of the fiber, and achieves the effect of protecting the carbon fiber. and the plurality of matrix resins are epoxy resins.

Epoxy resins have reactive epoxy functional groups, so that under appropriate catalysis, different types of curing agents (e.g., functional groups such as amines or acid anhydrides) can react and bond with each other to form tertiary It can be an original mesh structure. Epoxy resins are excellent thermosetting materials. In some embodiments, bisphenol A type epoxy resin can be utilized as the main component of the sizing agent.

Conventional sizing compositions include epoxy resins, acrylates (and/or methacrylates), and polyester resins with bisphenol A-type backbones and polyoxyethylene chains. However, its ester-based structure tends to adsorb moisture in the air, has a dipole-dipole bond stack arrangement, and generates adhesion between carbon fiber bundles. In addition, the double bond structure of the acrylic group may be crosslinked by a radical reaction, which accelerates the curing of the carbon fiber, making it difficult for the carbon fiber to stretch during the processing of composite materials, or by mechanical friction. Since it causes problems such as the tendency to generate fluff, the workability of the carbon fiber is lowered.

It is found that the hardening of the carbon fiber is due to the ring opening of the epoxy resin and the breakage of the double bond structure of the vinyl ester resin, resulting in a radical polymerization reaction. For example, the double bond undergoes a radical reaction upon exposure to sunlight and oxygen. In addition, after the reaction, a network-like steric cross-linking occurs between molecules to harden (harden), and subsequent machinability is reduced. Since the initiated radical reaction is a chain reaction and is always cyclic, the hardening of the carbon fibers can be delayed by delaying (or stopping) the occurrence of the radical reaction.

For carbon fiber curing, epoxy systems are found to be much slower than double bond radical reactions, as epoxy systems are affected only by epoxy concentration ([epoxy]) and ring-opening rates. Therefore, determining the hardening factor by the double bond, reaction rate=K*[VE]*[oxygen radical], where K is the Arrhenius reaction rate formula K=A*exp(−E/RT) and VE is is the resin concentration, the resin concentration and the open system oxygen radical concentration are both constants, the activation energy of the acrylic acid double bond is 124 KJ / mol, stored at 25 ° C., and each time the temperature rises by 10 ° C., the reaction The test temperature Tt and acceleration days are 5^[(Tt-25)/10] because the speed increases by a factor of 5.

In view of the problem that the above-mentioned sized carbon fibers tend to absorb moisture and cause tackiness and hardening over time, the bonding strength and machinability of the carbon fibers are further deteriorated. Therefore, the present disclosure provides a sizing agent for carbon fibers in order to solve the above problems. The sizing agent of the present disclosure strengthens the bonding force between the carbon fiber and the matrix resin, prevents the carbon fiber from fluffing and thread breakage during the processing process, suppresses hardening over time, and can be stored for a long time. Stability can be increased.

The sizing agent composition of the present disclosure includes a hindered phenolic reagent (D). The addition of the hindered phenolic reagent (D) provides hydrogen radicals to block chain reactions caused by oxygen radicals during the polymer curing process. In the process of forming the sizing agent of the present disclosure, the hindered phenolic reagent (D) produces relatively stable aromatic oxygen radicals, which have the ability to further scavenge active radicals, thus causing radical reactions. can be achieved to stop and retard the hardening of the carbon fibers.

Addition of a radical-scavenging inhibitor (for example, a hindered phenolic reagent (D)) can delay the occurrence of the radical reaction. Hindered phenols are radical reaction inhibitors. Referring to the reaction formula (I) below, the principle of action is that the hydroxyl groups (—OH) on the benzene ring of the hindered phenols are spaced on both sides. Since the alkyl group having a large hindrance is substituted, the hydrogen (H) atom is easily dropped from the molecule, and furthermore, it bonds with the radical to terminate the radical chain reaction and retard the curing.

The present disclosure comprises a resin main agent (A) comprising at least one epoxy group compound, a resin main agent (B) comprising at least one acrylate compound, a surfactant (C), and a hindered phenolic reagent (D). , and the balance of a solvent, and the sizing agent has a particle size of 0.01 to 0.5 μm. In some embodiments, the content of resin base (B), which consists of at least one acrylate compound, is the same as the content of surfactant (C).

The resin base (A) comprising at least one epoxy group compound of the sizing agent of the present disclosure includes a bisphenol A type epoxy compound, a bisphenol F type epoxy compound, a bisphenol S type epoxy compound, a phenol epoxy resin, or a combination thereof. In some embodiments, the epoxy equivalent weight of the resin base (A) comprising at least one epoxy group compound is between about 100 g/eq and about 1500 g/eq, such as between about 130 g/eq and about 1000 g/eq. or between about 160 g/eq and about 900 g/eq. An epoxy equivalent weight of less than about 100 g/eq enhances the degree of cure of fiber bundles (eg, carbon fiber bundles) over time. If the epoxy equivalent exceeds about 1500 g/eq, the bondability with the matrix resin is lowered.

In some embodiments, the content of the resin base (A) comprising at least one epoxy group compound is about 2 to about 30 parts by weight with respect to 100 parts by weight of the total weight of the sizing agent. In another embodiment, the content of the resin base (A) consisting of at least one epoxy group compound is about 10 to about 25 parts by weight, such as 12.5, 15, 17.5, 20, 22.5. weight part. When the content of the main resin (A) comprising at least one epoxy group compound is less than 2 parts by weight, the fiber bundles are loosened and softened. If the content of the main resin component (A) comprising at least one epoxy group compound is more than 30 parts by weight, it may affect the bondability with the matrix resin.

The bisphenol A type epoxy compound may be a commercially available product, for example, NPEL ^™ 127, NPEL ^™ 128, NPEL ^™ 134, NPEL ^™ 901, NPEL ^™ 902, NPEL ^™ 904 manufactured by Nana Plastic Industry Co.; EPON ^™ Resin 828, EPON ^™ Resin 830, EPON ^™ Resin 834, and EPON ^™ Resin 1001F manufactured by Changchun Human Resin Factory; BE ^™ 114, BE ^™ 186, and BE ^™ 188 manufactured by Changchun Human Resin Factory; , ADEKA Resin EP-4300 and ADEKA Resin EP-4700.

The bisphenol F type epoxy compound may be a commercial product, for example, NPEL ^™ 170 manufactured by Nana Plastic Industry Co., Ltd.; EPON ^™ Resin 869 manufactured by HEXION; jER ^™ 806 and jER ^™ 807 manufactured by Mitsubishi Chemical; Epoxy compounds such as BE ^™ 170, BE ^™ 235 and BE ^™ 283 manufactured by Changchun Artificial Resin Factory.

The bisphenol S-type epoxy compound may be a commercially available product, and examples thereof include epoxy compounds such as 185S and 300S manufactured by Compton.

The phenol epoxy resin may be a commercially available product, for example, NPEL ^™ 630, NPEL ^™ 638, NPEL ^™ 640 manufactured by Nana Plastic Industry Co., Ltd.; NPCN ^™ 701, NPCN ^™ 702, NPCN manufactured by Nana Plastic Industry Co. ⁷⁰³ , NPCN ^TM 704, NPCN ^{TM 704L ; H} , HF-series manufactured by ^Meiwa Kasei Co., Ltd ^.; Epoxy compounds such as ^TM 177 can be mentioned.

The resin main component (B) composed of at least one acrylate compound of the sizing agent of the present disclosure includes acrylate having an oxyalkylene group in the molecule, methacrylate having an oxyalkylene group in the molecule, acrylate having an oxyalkyl group in the molecule, Methacrylates with intramolecular oxyalkyl groups, acrylates without intramolecular oxyalkylene groups, methacrylates without intramolecular oxyalkylene groups, acrylates without intramolecular oxyalkyl groups, intramolecular oxyalkyl groups methacrylate, or combinations thereof.

In some embodiments, the content of the resin base (B) consisting of at least one acrylate compound is about 2 to about 30 parts by weight based on 100 parts by weight of the total weight of the sizing agent. In another embodiment, the content of the resin base (B) consisting of at least one acrylate compound is about 10 to about 25 parts by weight, such as 12.5, 15, 17.5, 20, 22.5 parts by weight. Department. If the content of the main resin component (B) comprising at least one acrylate compound is less than 2 parts by weight, the bondability with the matrix resin may be affected. If the content of the resin main component (B) comprising at least one acrylate compound is more than 30 parts by weight, the fiber bundle will be difficult to bundle or too soft.

The resin main component (B) comprising at least one acrylate compound may be a commercially available product, for example, acrylate compounds such as QualiCure ^™ GM62S70, QualiCure ^™ GM62V20, QualiCure ^™ GM62V40, and QualiCure ^™ GM62V60 manufactured by Kokusei Chemical Co., Ltd. mentioned.

Surfactants (C) of the sizing agents of the present disclosure include nonionic surfactants, anionic surfactants, cationic surfactants, or combinations thereof. In some embodiments, nonionic surfactants can be used in combination with either anionic surfactants or cationic surfactants.

In some embodiments, the content of surfactant (C) is about 0.5 to about 15 parts by weight based on 100 parts by weight of the total weight of the sizing agent. Also, in other embodiments, the content of surfactant (C) is from about 5 to about 12.5 parts by weight, such as 6.5, 8, 9.5, 11 parts by weight. If the content of the surfactant (C) is less than 0.5 parts by weight, the emulsifying effect will not be obtained. If the content of the surfactant (C) is more than 15 parts by weight, the processability of the fiber bundle will deteriorate.

Nonionic surfactants may be, for example, aliphatic nonionic surfactants or aromatic nonionic surfactants. Types of aliphatic nonionic surfactants include, for example, higher alcohol ethylene oxide additives, polyol polyoxyethylene ethers, carbon 16-18 alcohol polyoxyethylene ethers, alkyl polyoxyethylene ethers, polyethylene glycol fatty acid esters, and the like. good. Aromatic nonionic surfactants may be, for example, polyethylene glycol octylphenyl ether, polyethylene glycol nonylphenyl ether, polyethylene glycol bisphenol A derivatives, and the like.

Anionic surfactants may be, for example, sulfates, sulfonates or phosphates. Sulfuric acid esters include, for example, higher alcohol sulfates, higher alkyl polyethylene glycol ether sulfates, polycyclic phenyl ether polyethylene glycol ether sulfates, and the like. Examples of sulfonates include alkylbenzenesulfonates, polycyclic phenyl ether sulfonates, alkylsulfonates, and dialkylsulfosuccinates. Phosphates include, for example, polyethylene glycol nonylphenyl phosphate, polyoxyethylene alkylphenyl ether phosphate triethanolamine salt, polyethylene glycol styrenated aryl ether phosphate, and the like.

Examples of cationic surfactants include quaternary ammonium salts such as alkyldimethylbenzene quaternary ammonium salts, alkyltrimethylammonium quaternary ammonium salts, dialkyldimethyl quaternary ammonium salts, ester quaternary ammonium salts, and imidazoline quaternary ammonium salts. good.

ヒンダードフェノール系試薬（Ｄ）としては、市販品であってよく、例えば、Ｅｖｅｒｌｉｇｈｔ Ｃｈｅｍｉｃａｌ製のＥｖｅｒａｏｘ（商標）１０１；ＡＯ－１１３５又はＸＰ－６９０が挙げられる。具体的には、Ｅｖｅｒａｏｘ（商標）１０１は、式（ＩＩ－１）で表される構造式（ｎが７～９である）を有する。ＡＯ－１１３５は、式（ＩＩ－２）で表される構造式を有する。

The hindered phenolic reagent (D) of the sizing agent of the present disclosure may have a structural formula represented by Formula (II), where R is a long carbon chain ester.

Hindered phenolic reagents (D) may be commercially available, such as Everaox™ 101; AO-1135 or XP-690 from Everlight Chemical. Specifically, Everaox™ 101 has a structural formula (where n is 7 to 9) represented by formula (II-1). AO-1135 has a structural formula represented by formula (II-2).

Specifically, the hydroxyl group (--OH) on the benzene ring of the hindered phenols is substituted with alkyl groups with large steric hindrance on both sides, so the hydrogen (H) atom is likely to drop out of the molecule, and further radical It binds with to terminate the radical chain reaction and has the effect of delaying curing.

In some embodiments, the content of the hindered phenolic reagent (D) is about 0.01 to about 0.5 parts by weight relative to 100 parts by weight of the total weight of the sizing agent. 1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 parts by weight. Also, in other embodiments, the content of the hindered phenolic reagent (D) is about 0.05 to about 0.1 parts by weight, such as 0.06, 0.07, 0.08, 0. 0.09 parts by weight. If the content of the hindered phenol-based reagent (D) is less than 0.01 parts by weight, it will be difficult to terminate the radical chain reaction, and thus the curing of the carbon fibers will not be delayed. When the content of the hindered phenolic reagent (D) is greater than 0.5 parts by weight, there is no beneficial effect in delaying the hardening of carbon fibers.

The solvent for the sizing agents of the present disclosure may be deionized water. In some embodiments, the solvent content of the sizing agent is from about 25 to about 95.5 parts by weight, such as 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95 parts by weight. In some embodiments, the sizing agent of the present disclosure is applied to carbon fibers in the form of a dispersion in water and does not contain any organic solvent.

The apparatus for producing the sizing agent of the present disclosure produces a carbon fiber sizing agent in which the emulsion type is uniformly dispersed by mechanical shearing force. In some embodiments, the device may be a paddle-type agitator impeller, and the impeller shape may be dissolving, trilobal, or tetralobal. In another embodiment, the device also incorporates anchored stirrer blades. In some embodiments, sizing agents for carbon fibers may be produced by devices such as ultrasonic homogenizers, high speed homogenizers, high speed emulsifiers, and the like.

The sizing agent of the present disclosure is an aqueous solution that is self-emulsified and/or emulsified and dispersed in water, and has an average particle size of less than 1 μm, such as about 0.01 to about 0.5 μm, such as 0.05 μm. , 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 μm. If the average particle size is larger than 1 μm, the sizing agent cannot be uniformly adhered to the carbon fibers, and the free energy of the particles is insufficient for Brownian motion, which may result in sedimentation, resulting in poor storage stability.

<Particle size analysis of sizing agent>

The average particle size of the sizing agent is measured by the laser light scattering principle. When a laser beam is irradiated into a particle solution, the particles in the solution scatter the laser beam. Depending on the size, the degree of Brownian motion of the particles is different, so the degree of scattering of the laser beam is also different. A size distribution is computed. In some embodiments of the present disclosure, the average particle size measurement of the sizing agent is performed by a Brookhaven Nanobrook Omni instrument.

<Application of sizing agent to carbon fiber>

The sizing agent of the present disclosure is sized onto the carbon fiber surface in an impregnated form. Carbon fiber TC35R-24K (manufactured by Taiwan Plastic Industry Co., Ltd., TARIFIL, total of 24000 single fibers, single fiber strength of about 4000 MPa, single fiber module 240 GPa) not coated with a sizing agent is immersed in an immersion tank containing a sizing agent, and further A heat drying treatment is performed at about 100 to 250° C., and the drying time is about 2 to 10 minutes. If the temperature is less than 100°C, water cannot completely evaporate. If the temperature is higher than 250°C, the sizing agent undergoes a thermal reaction and deteriorates. As for the heat drying method, a heating method such as a hot air method, a hot roll contact method, or an infrared heating method may be appropriately adopted, or the above two or three methods may be used together and wound into a roll.

The above emulsion-type carbon fiber sizing agent can be used as an interface layer that connects the carbon fibers and the matrix resin in the carbon fiber composite material. In some embodiments, the weight of the sizing agent is about 0.1 to about 5 weight percent, such as about 0.5 to about 3 weight percent, such as 1, 1 . 5, 2, 2.5% by weight. If the sizing amount is less than 0.1% by weight, the sizing agent cannot provide the carbon fibers with good cohesiveness, interfacial bonding strength with the matrix resin, and abrasion resistance. If the sizing amount exceeds 5% by weight, it is difficult for the carbon fibers to spread, and it is difficult to stretch the threads in the subsequent processing and molding of the composite material.

<Evaluation of sizing rate of carbon fiber>

Take a 1 meter (m) long carbon fiber bundle treated with a sizing agent, weigh its weight W1, and then place it in an oven at about 400° C. to bake and remove the sizing agent, and after about 40 minutes It is taken out and its weight W2 is weighed after the temperature is recovered for about 10 minutes, and the sizing rate of the carbon fiber is (W2-W1)/W1*100%. In some embodiments, the carbon fiber sizing percentage is from about 0.1 to about 5 weight percent, such as from about 0.5 to about 3 weight percent. Incidentally, the sizing rate of Comparative Examples and Examples 1 to 5 in this specification is fixed at 1.0±0.2% by weight.

<Evaluation of hygroscopicity of sizing agent>

A carbon fiber bundle (fiber bundle 1) having a length of 5 centimeters (cm) not treated with a sizing agent is taken, and its weight W3 is weighed. Furthermore, 5 cm of the carbon fiber bundle (fiber bundle 2) treated with the sizing agent is taken, and its preweight W4 is weighed. The fiber bundle 1 and the fiber bundle 2 are placed in a constant temperature and humidity environment bath of about 70° C. and a humidity of about 85% RH. . Moisture absorption % of sizing agent=[(W6-W4)-(W5-W3)]/W4*100%. In some embodiments, the sizing agent has a moisture absorption rate of less than about 0.05%, such as 0.01, 0.02, 0.03, 0.04%.

<Detection of fluff on carbon fiber>

Reference is made to FIG. 1, which is a schematic diagram of an apparatus 100 for detecting carbon fiber fuzz. Take a 100-meter-long carbon fiber bundle 110 treated with a sizing agent, rub it with seven metal rollers 120 (no transmission, no special surface treatment) with a tension of 600 cN, and put a sponge behind the metal roller 120 A pad 130 is provided to collect fluff due to wear of the carbon fiber bundles 110 . Finally, the fluff is dried at a temperature of about 105° C. for about 40 minutes and the fluff is weighed (unit: mg).

<Detection of hardness of carbon fiber>

2A and 2B, which are schematic diagrams of an apparatus 200 for detecting the hardness of carbon fibers. Specifically, FIG. 2A is a schematic diagram before the carbon fiber bundles are biased by the biasing source 210, and FIG. 2B is a schematic diagram after the carbon fiber bundles are biased by the biasing source 210. be. The carbon fiber bundle 110 treated with a sizing agent is laid on a platform 220 having a gap 230, the carbon fiber bundle 110 is bent by the biasing force of the biasing source 210, and the force required to push down to a predetermined depth is the hardness of the carbon fiber. (unit: g). The gap 230 of the carbon fiber hardness sensing apparatus of the present disclosure is approximately 5 millimeters (mm).

<Detection of change over time in carbon fiber>

The carbon fiber bundle is placed in a constant temperature and humidity environment box with a humidity of about 70 ° C. and a humidity of about 85% RH for accelerated curing. Fiber fluff detection and carbon fiber hardness detection are performed.

<Preparation of sizing agent of comparative example>

The resin main agent (A) comprising at least one epoxy compound, the resin main agent (B) comprising at least one acrylate compound and the surfactant (C) are heated to a temperature higher than the melting point of the resin main agent (A) and the resin main agent (B). After uniformly mixing with an IKA mixer, the temperature of the mixed state is lowered to the cloud point temperature of the surfactant (C), water is added dropwise over 6 hours at a rotation speed of about 5000 to about 10000 rpm, and the mixture is uniformly mixed. An emulsified and dispersed solution, ie, a comparative sizing agent, can be obtained. The particle size (Dv50; nm) of the sizing agent of the comparative example is about 0.01 to about 0.5 μm. The melting points of the main resin (A) and the main resin (B) are about 60°C to about 95°C. Surfactant (C) has a cloud point temperature of about 60°C to about 70°C.

<Preparation of sizing agents of Examples>

The resin main agent (A) comprising at least one epoxy compound, the resin main agent (B) comprising at least one acrylate compound and the surfactant (C) are heated to a temperature higher than the melting point of the resin main agent (A) and the resin main agent (B). After uniformly mixing with an IKA stirrer, the mixed state is cooled to the cloud point temperature of the surfactant (C), and then water is added dropwise over 6 hours at a rotation speed of about 5000 to about 10000 rpm to uniformly emulsify. A dispersed solution can be obtained, and finally the hindered phenolic reagent (D) can be added to obtain the sizing agents of Examples (Examples 1 to 5). The particle size (Dv50; nm) of the sizing agents of the examples is about 0.01 to about 0.5 μm. The melting points of the main resin (A) and the main resin (B) are about 60°C to about 95°C. Surfactant (C) has a cloud point temperature of about 60°C to about 70°C.

In some alternative embodiments, the hindered phenolic reagent (D) is mixed with the resin base (A), the resin base (B) and the surfactant (C), and then carried out in the same manner as described above. Example sizing agents may be formed.

Test example: Evaluation of hardness of carbon fiber and aging of carbon fiber

According to the recipe of the composition in Table 1 below, the sizing agents of Comparative Examples and Examples 1 to 5 were prepared with reference to the preparation of the sizing agents of Comparative Examples and Examples above.

The sizing agent based on Table 1 above was subjected to a carbon fiber hardness test and a carbon fiber aging test, and the test results are shown in Table 2 below. As is clear from Table 2, by applying a sizing agent containing a hindered phenol-based reagent (D) to carbon fibers, the amount of fluff on the carbon fibers was reduced and the hardness of the carbon fibers was also improved compared to the comparative examples. bottom.

For example, on the 7th day and 14th day of elapsed time, the amounts of fluff in Examples 1 to 5 are all smaller than the amount of fluff in Comparative Example. Specifically, the amount of increase in fluff in Examples 1 to 5 is smaller than the amount of increase in fluff in Comparative Example. Also in the aging test, the amount of change in hardness of the carbon fibers of Examples 1 to 5 is smaller than the amount of change in hardness of the carbon fibers of Comparative Example.

See Table 2 below for details. In the comparative example, the hardness of the carbon fiber after 0 days of elapsed time was about 13 g, whereas the hardness of the carbon fiber after 14 days of elapsed time was about 39 g, an increase of about 200%. In Examples 2 to 5, the hardness of the carbon fiber on the 0th day of aging is about 13 g, while the hardness of the carbon fiber on the 14th day of aging is about 26 g, and the hardness is about 100%. Increased.

Since the sizing agent of the present disclosure contains a hindered phenolic reagent (D), it solves the problem of moisture absorption and adhesiveness of the originally sized carbon fiber, thus suppressing the problem of hardening over time, and the carbon fiber bundle It has the effect of prolonging the curing time of. The sizing agent of the present disclosure strengthens the bonding force between the carbon fiber and the matrix resin, prevents the occurrence of fluff and thread breakage in the carbon fiber processing process, suppresses hardening over time, and prevents mechanical processing. It is possible to prevent deterioration of the properties.

As described above, the present disclosure has been disclosed in the above embodiments, but the embodiments do not limit the present disclosure, and a person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure. Therefore, the protection scope of this disclosure should be based on what is defined by the claims.

REFERENCE SIGNS LIST 100 Carbon fiber fluff detection device 110 Carbon fiber bundle 120 Metal roller 130 Ponzi pad 200 Carbon fiber hardness detection device 210 Source of force 220 Platform 230 Gap

Claims (10)

Per 100 parts by weight of the total weight of the sizing agent,
a resin main agent (A) comprising 2 to 30 parts by weight of at least one epoxy group compound;
a resin main agent (B) comprising 2 to 30 parts by weight of at least one acrylate compound;
0.5 to 15 parts by weight of a surfactant (C);
0.01 to 0.5 parts by weight of a hindered phenolic reagent (D);
a remaining solvent; and
A sizing agent for carbon fibers, wherein the sizing agent has a particle size of 0.01 to 0.5 μm. 2. The resin base material (A) comprising at least one epoxy group compound according to claim 1, wherein the resin main component (A) comprises a bisphenol A type epoxy compound, a bisphenol F type epoxy compound, a bisphenol S type epoxy compound, a phenol epoxy resin, or a combination thereof. Sizing agent for carbon fiber. The sizing agent for carbon fiber according to claim 1, wherein the resin main component (A) comprising at least one epoxy group compound accounts for 10 to 25 parts by weight. The resin main component (B) comprising at least one acrylate compound includes acrylates having an oxyalkylene group in the molecule, methacrylates having an oxyalkylene group in the molecule, acrylates having an oxyalkyl group in the molecule, and oxyalkyl groups in the molecule. a methacrylate having a group, an acrylate having no oxyalkylene group in the molecule, a methacrylate having no oxyalkylene group in the molecule, an acrylate having no oxyalkyl group in the molecule, a methacrylate having no oxyalkyl group in the molecule, or The carbon fiber sizing agent according to claim 1, comprising combinations thereof. The sizing agent for carbon fiber according to claim 1, wherein the resin main component (B) comprising at least one acrylate compound accounts for 10 to 25 parts by weight. The carbon fiber sizing agent according to claim 1, wherein the surfactant (C) comprises a nonionic surfactant, an anionic surfactant, a cationic surfactant, or a combination thereof. The sizing agent for carbon fiber according to claim 1, wherein the surfactant (C) accounts for 5 to 12.5 parts by weight. The sizing agent for carbon fiber according to claim 1, wherein the hindered phenol-based reagent (D) accounts for 0.05 to 0.1 parts by weight. Carbon fibers coated with the carbon fiber sizing agent according to claim 1, wherein the sizing rate is 0.1 to 5% by weight. The carbon fiber coated with the sizing agent for carbon fiber according to claim 1, having a hardness increase of less than 100% after a change over time of 14 days is detected.

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