KR102288735B1 - Carbon fiber bundles and method of manufacturing the same - Google Patents

Abstract

The present invention relates to a carbon fiber bundle produced through a carbon fiber, a sizing agent, and a drying process thereof. The present invention is characterized in that the sizing agent is composed of an epoxy resin and an EO additive therefor, so that the viscosity is 6 to 8 x 10 ⁶ cP at 25 ° C., 800 to 3000 cP at 100 ° C., and the elasticity is 2.5 to 5.3 at 100 ° C. , The drying process is characterized in that, after impregnating carbon fibers in resin, the bundling and opening properties are improved through a two-step process through a hot air dryer and a heating roller. An object of the present invention is to provide a carbon fiber bundle suitable for

Description

Carbon fiber bundles and method of manufacturing the same

The present invention relates to a carbon fiber bundle and a method for manufacturing the same, and more specifically, a sizing agent having viscoelasticity is applied to the carbon fiber bundle, and through a two-step drying method, the bundling and openability are increased to provide excellent handling and impregnation properties. It relates to a carbon fiber bundle for a carbon fiber composite material and a method for manufacturing the same.

Carbon fibers have low elongation, and breakage of single fibers or fluff (fluff) is easy to occur due to mechanical friction or the like. Therefore, handling can be improved by providing a sizing agent to the carbon fiber.

And, in the manufacture of carbon fiber composite materials, a sizing agent such as an epoxy resin or a urethane resin is mainly used in order to improve the adhesion properties between the carbon fiber and the thermosetting matrix resin.

According to the components of the sizing agent, the bundling and openability of the carbon fiber bundles are changed.

However, since the cohesion and openness have characteristics that are compatible with each other, it is difficult to improve them at the same time.

As described above, among the properties of carbon fibers, bundling and openability are compatible with each other, but there is a problem in that it is difficult to improve them at the same time.

Accordingly, the present invention is to solve such problems in the prior art, and by applying a sizing agent having viscoelasticity to the carbon fiber bundle and by a two-step drying method, the bundling and openability are improved, and handling and openability using the carbon fiber bundle An object of the present invention is to provide a carbon fiber bundle suitable for use as a reinforcing material of a thermosetting resin having excellent impregnation property and a method for manufacturing the same.

The present invention for achieving the above object, in the carbon fiber bundle to which a sizing agent is given, the sizing agent consists of a resin and an additive thereto, and the resin includes two or more epoxy groups or high molecular weight epoxy and poly It contains an epoxy-based resin that is a compound mixed with an ester, and the additive provides a carbon fiber bundle, characterized in that the epoxy-based ethylene oxide.

In addition, the carbon fiber bundle impregnated with the sizing agent is dried with a primary hot air dryer and dried with a secondary heating roller to provide a method for producing a carbon fiber bundle having improved bundling properties and opening phase.

The carbon fiber bundle to which the sizing agent having viscoelasticity of the present invention is imparted and the method for manufacturing the same have improved bundling and openability, so that when manufacturing a composite material using the carbon fiber bundle, the handleability of the composite material is improved, and the matrix resin is It has the effect of contributing to productivity improvement by expressing excellent impregnation property.

1 is a schematic diagram showing a sizing agent application and primary drying process according to the present invention.
FIG. 2 is a schematic diagram illustrating a secondary process after the primary drying process of FIG. 1 .
3 is a perspective view of an uneven roll used in the process of FIG. 1 .
FIG. 4 is a cross-sectional view taken along line AA of the concave-convex roll shown in FIG. 3 .
5 is a schematic diagram of drape evaluation according to the present invention.

Hereinafter, the present invention will be described in detail. However, the following contents are exemplified to explain the present invention, and the present invention is not limited thereto.

In the present invention, in the carbon fiber bundle provided with a sizing agent, the sizing agent consists of a resin and an additive thereto, and the resin is a compound containing two or more epoxy groups or a mixture of high molecular weight epoxy and polyester. Including a resin-based, the additive relates to a carbon fiber bundle using an epoxy-based ethylene oxide.

In addition, in the present invention, in the method for producing a carbon fiber bundle to which the sizing agent is provided, the sizing agent includes an epoxy resin which is a compound containing two or more epoxy groups or a mixture of a high molecular weight epoxy and polyester, and the epoxy Carbon fiber bundles with improved bundling and openability, characterized in that by adding additional ethylene oxide to obtain a sizing agent mixture, impregnating carbon fibers therein, drying with a primary hot air dryer, and drying with a secondary heating roller It relates to a manufacturing method of

When manufacturing composite materials such as prepreg, fabric, pultrusion, and filament winding using the carbon fiber bundle of the present invention, the carbon fiber composite exhibits excellent effects due to the improvement of handling and impregnation properties of the composite material Carbon fiber bundles for materials can be manufactured.

The production of carbon fiber bundles for carbon fiber composite materials with excellent handling and impregnation properties is realized through a sizing agent. That is, when the bundling and openability of the carbon fiber bundle is excellent, the handling and impregnation properties of the carbon fiber composite material manufactured using the same are excellent. The viscoelasticity and viscosity of the agent should be adjusted.

If the viscosity is increased by controlling the component and content of the sizing agent, the cohesion between the carbon fiber and the carbon fiber is increased. fidelity will increase.

In the present invention, a sizing agent having viscoelastic properties (DMA properties) is selected, and a carbon fiber bundle suitable for use as a reinforcement of a thermosetting resin, etc. can be manufactured through a sizing agent application and a two-step drying method.

[Composition of sizing agent]

The sizing agent used for the carbon fiber bundle suitable for use as a reinforcing material of the thermosetting resin of the present invention may be composed of a resin and an additive thereto.

The resin may include two or more epoxy groups, or may be composed of an epoxy-based compound in which a high molecular weight epoxy and polyester are mixed.

In addition, an epoxy-based ethylene oxide (Ethylene Oxide, EO, hereinafter referred to as EO) adduct may be used as the additive, and the additive is preferably contained in less than 30% by mass with respect to the resin composition of the sizing agent, more preferably It should contain 10 mass % or more and less than 25 mass %.

If the amount of the epoxy-based EO as the additive is 10% by mass or less, the carbon fiber has a strong bundling property, so that the expandability is lowered and the openability may be lowered.

The sizing agent is preferably emulsified in water and used in the form of an aqueous sizing solution, and when the sizing agent is applied to carbon fibers, the sizing agent is diluted in water and impregnated with an aqueous sizing solution and then dried.

Therefore, the sizing agent is characterized in that the viscosity of the epoxy resin is 6-8×10 ⁶ cP at 25° C., 800-3,000 cP at 100° C., and the elasticity (Tan δ) value is 2.5-5.3 at 100° C. do.

[Sizing agent application and drying process]

The present invention is carried out through a total of two drying steps, and the state of the sizing agent is not completely solidified and exhibits viscoelasticity. Due to these fluid properties, the carbon fiber bundle exhibits a property of spreading the filaments by pressure or heat.

In particular, since one-way prepreg manufacturing is an operation of impregnating a resin with a fiber to form a thin sheet, the property of uniformly spreading the carbon fiber bundles, that is, openability, is required for uniform resin impregnation.

In general, when the viscosity of the sizing agent is low, the opening property is advantageous, but the bundling property is lowered and the handling property is poor.

However, even if the same sizing agent is used, the bundling and opening properties are changed according to the impregnation and drying methods. If a heating roller is used as in contact drying, the sizing agent dries only on the surface and the bundling property is increased, so opening is not good. have compatible properties.

Therefore, the drying method of the sizing agent in the present invention is characterized in that the bundling and openability between carbon fibers are secured at the same time by selecting a drying method by appropriately mixing a hot air dryer and a heating roller. Specifically, after giving the sizing agent to the carbon fiber,

First, using a hot air dryer, the moisture in the sizing agent was volatilized and the sizing agent was dried evenly between the carbon fibers, and secondarily, it was heat-treated using a heating roller to widen the fiber surface to facilitate opening.

The temperature of the primary hot air dryer is preferably dried within 30 seconds to 180 seconds in a temperature range of 90 °C or higher and 120 °C or lower for the purpose of volatilizing moisture. When the temperature is below 90 ℃, the volatilization rate of moisture is significantly slowed down, and the drying efficiency of the sizing agent is lowered.

If the residence time of the first hot air dryer is shorter than 30 seconds, the drying ends before the sizing agent starts to evaporate, and the desired sizing adhesion amount may not be obtained. When the carbon fiber bundle is dried, the equipment becomes large and the equipment cost increases.

The secondary heating roller is carried out for the purpose of heat-treating the sizing agent in which the moisture has evaporated, and it is preferable to dry it within 10 seconds to 180 seconds in a temperature range of 150 ℃ or more and 200 ℃ or less. When the temperature is 150 ° C. or less, there is a problem that the high-order processability is deteriorated due to insufficient solidification of the sizing agent, and thus the high-order workability is deteriorated. If the residence time of the secondary heating roller is shorter than 10 seconds, it is difficult to expect the heat treatment effect of the sizing agent, and on the contrary, if it is longer than 180 seconds, the heating roller for heat treatment of the sizing agent is required a lot, the equipment cost is excessive, and the fiber tension is high problems arise.

In order to understand the present invention more specifically, the drying process of the present invention will be described with reference to the accompanying drawings.

First, as shown in FIG. 1 , the surface-treated carbon fiber 100 is introduced through the sizing aqueous solution impregnator 110 . After passing through the sizing dipping roll 116, the sizing aqueous solution 114 is impregnated into the carbon fiber. The carbon fiber that has passed through the sizing aqueous solution impregnator 110 passes through the hot air dryer 130 as a primary drying treatment step. After that, as the secondary drying step, it passes through the heating roller 140 shown in FIG. 2 and moves to the winder 150, and the drying process is completed.

[Experimental example]

In the present invention, a sizing agent with viscoelasticity is applied to carbon fibers, and the sizing agent viscoelasticity is measured because it is intended to increase the bundling and openability of the carbon fiber bundle by passing it through a drying step through a hot air dryer and a heating roller, An experiment was conducted to evaluate the bundling and openability of the carbon fiber bundle to which the sizing agent was applied.

1. Measurement of sizing agent viscoelasticity

The sizing agent is in a liquid state in which the resin component, emulsifier, and smoothing agent are emulsified. After drying and removing moisture, use a rheometer (Rheometer; Anton Paar, MCR-301) at a shear rate of 5 °C/min. Viscoelastic properties were measured from room temperature to 110 °C. From this, the viscosity and elasticity (E′ (storage modulus), E″ (loss modulus) and Tan δ) were obtained.

The sizing agent used as a comparative example in an experiment to measure the viscoelasticity of the sizing agent used 100% by mass of an epoxy resin, and the sizing agent used in Examples 1 to 3 was added to the epoxy EO adduct to the resin composed of epoxy and polyester. . The mixing mass ratio is shown in Table 1 below (sizing agent composition and viscoelasticity results).

As a result of measuring the viscoelasticity of the sizing agent, it was found that Tan δ of Examples 1, 2, and 3 increased compared to Comparative Examples, which is the sizing when an epoxy-based EO adduct is added to a resin consisting of an epoxy and a polyester component. It means that the elastic modulus of the agent increases.

The viscosity and elastic modulus of the sizing agent change depending on the components (resin content, molecular weight, and additive content) of the sizing agent, and as the temperature of the sizing agent increases, the viscosity and elastic modulus decrease. Since the viscosity and elastic modulus of the sizing agent affect the bundling and openability of carbon fibers, it is preferable to select an appropriate range. If the viscosity of the sizing agent is too high, the bundling property of the carbon fiber may be excellent, but the openability may be deteriorated.

2. Evaluation of the bundling properties of carbon fiber bundles provided with a sizing agent

A carbon fiber bundle is composed of thousands to tens of thousands of filaments, and is treated as a bundle as a single tow. The bundle of carbon fibers has a hard touch feeling when the bundling property is high, and a soft touch feeling when the bundling property is low. This cohesion is evaluated by measuring the drape. The drape measurement method is described with reference to the drape schematic diagram shown in FIG. 5 , and after leaving 1000 m carbon fiber under a load of 50 g for 30 minutes, the length is cut to 350 mm (L). After fixing one end of the carbon fiber (200) 350 mm on the acrylic box having a height (h) of 300 nm with 20 mm tape, measure the free-fall distance 220 with a ruler in mm unit 50 times to calculate the average value .

The drape evaluation results of the carbon fiber bundles are shown in [Table 2] below.

3. Evaluation of openability of carbon fiber bundles provided with sizing agent

The openability of the carbon fiber bundle was evaluated by measuring the open yarn width. As a device for widening the carbon fiber bundle, 5 stainless steel rods with a smooth surface of 10 nm in diameter are spaced 5 cm apart and the carbon fibers are run in the zigzag direction at a contact angle of 120 degrees with the stainless steel rod, and the carbon fibers are stretched 3 m apart. run at a speed of /min. Carbon fiber is passed through the five rods, the widened yarn width is detected from the laser sensor, and the average opened yarn width and CV % are calculated from 5000 data.

The comparative example used in the experiment to evaluate the bundling and openability of the dried carbon fiber bundle after the sizing agent of the present invention was applied was wound by passing only the hot air dryer after sizing impregnation, and referring to FIGS. 1 and 2, Example 1 After sizing impregnation, 3 passes through a hot air dryer 130 as a primary drying step and a heating roller 140 as a secondary drying step, followed by a two-step drying process of winding 150 .

The measurement result of the open yarn width of the carbon fiber bundle is shown in [Table 2] (characteristics of the carbon fiber bundle dried after application of the sizing agent and the quality when prepreg is applied).

When the present invention analyzes the results of manufacturing the prepreg, which is a carbon fiber composite material, using a carbon fiber bundle, when the drying step used in the comparative example is passed, the fairness of the prepreg is deteriorated, and the production is impossible due to poor hair. However, when the two-step drying process of Examples 1 to 3 of the present invention was performed, the processability was improved, the wool was excellent, and the number of gaps was significantly reduced.

Therefore, the carbon fiber bundle, which has undergone a two-step drying process that can improve the bundling and openability by selecting the sizing agent component with viscoelasticity of the present invention, is said to have improved handling and excellent impregnation properties in manufacturing the prepreg. A conclusion was drawn.

100: carbon fiber after surface treatment 110: sizing aqueous solution impregnator
111: sizing aqueous solution supply line 112: sizing aqueous solution supply device
113: sizing aqueous solution transfer pump 114: sizing aqueous solution
115: sizing aqueous solution circulation roll 116: sizing dipping roll
117: sizing aqueous solution circulation line 118: roll
119: nip roll 120: uneven roll
123: guide rod 130: hot air dryer
140: heating roller 150: winder
200: initial carbon fiber 210: carbon fiber after free fall
220: drape length

Claims (9)

In the carbon fiber bundle to which the sizing agent is given, the sizing agent consists of a resin and an additive thereto, and the resin includes an epoxy-based resin that contains two or more epoxy groups or is a mixture of high molecular weight epoxy and polyester. And, the additive is epoxy-based ethylene oxide,
The carbon fiber bundle is passed through a hot air dryer to evaporate the moisture in the sizing agent primary drying; and secondary drying to widen the surface of the carbon fiber bundle through a heating roller; through the steps,
The temperature of the hot air dryer is dried within 30 seconds to 180 seconds at 90° C. or higher and 120° C. or lower, and the temperature of the heating roller is dried within 10 seconds to 180 seconds at 150° C. or higher and 200° C. or lower.
A carbon fiber bundle, characterized in that. The carbon fiber according to claim 1, wherein the epoxy resin has a viscosity of 6 to 8 x 10 ⁶ cP at 25 °C, 800 to 3000 cP at 100 °C, and a Tan δ value of 2.5 to 5.3 at 100 °C. bunch. [Claim 3] The carbon fiber bundle according to claim 1 or 2, wherein the additive is added in an amount of less than 10 to 30 mass% based on the epoxy resin. delete delete In the method for producing a carbon fiber bundle provided with a sizing agent,
The sizing agent contains two or more epoxy groups, or contains an epoxy-based resin that is a compound mixed with high molecular weight epoxy and polyester, and adds an epoxy-based ethylene oxide additive to obtain a sizing agent mixture,
After impregnating carbon fiber here, it is dried with a primary hot air dryer to volatilize moisture in the sizing agent, and then dried with a secondary heating roller to widen the carbon fiber bundle,
The temperature of the hot air dryer is 90 ℃ or more and 120 ℃ or less to dry within 30 seconds to 180 seconds, and the temperature of the heating roller is to dry within 10 to 180 seconds at 150 ° C or more and 200 ° C or less.
A method for producing a carbon fiber bundle, characterized in that. According to claim 6, wherein the sizing agent, the viscosity of the epoxy resin is 6 ~ 8 x 10 ⁶ cP at 25 ℃, 800 ~ 3000 cP at 100 ℃, Tan δ value is 2.5 ~ 5.3 at 100 ℃ characterized in that A method for producing a carbon fiber bundle. The method of claim 6 or 7, wherein the additive is added in an amount of less than 30% by mass based on the epoxy resin. delete

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