JPH07145549A - Application of sizing to carbon fiber - Google Patents

Abstract

PURPOSE:To suppress the formation of a sizing liquid film between adjacent yarns and remarkably decrease the uneven application of a sizing agent by immersing carbon fiber yarns in a sizing agent liquid and blowing compressed gas against the yarns at a specific flow rate. CONSTITUTION:Non-twisted carbon fiber yarns 2 are transferred through a roller 1 and immersed in a sizing liquid 3 composed of a solution or a dispersion of a sizing agent. The formation of a liquid film between adjacent yarns is prevented by blowing a normal temperature compressed air flow through small nozzles of a pipe 4 placed several cm above the yarns 2 at a flow rate between 0.5 and 10m/sec and higher than the surface tension of the liquid.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for applying a sizing agent to carbon fibers.

[0002]

2. Description of the Prior Art Carbon fiber has excellent mechanical, chemical,
Due to its electrical properties and weight reduction, it is widely used in various applications, such as structural materials for aerospace such as aircraft and rockets, sports equipment such as tennis rackets, golf shafts, fishing rods, etc., as well as transportation machinery such as ships and automobiles. It is about to be used in fields such as applications. By the way, since carbon fibers are inherently rigid and brittle, and have poor bending resistance and scratch resistance, contact with rollers, rubbing with a yarn guide, or time-dependent Fluffing is likely to occur due to rubbing with lure or various bending operations, and sometimes thread breakage may occur. For this reason, the carbon fibers are generally treated with various sizing agents, whereby the carbon fibers are made to have a bundling property, and bending resistance and abrasion resistance are generally improved.

However, if there is fluff before applying the sizing agent, the sizing liquid excessively adheres to the fluff, and sizing adhesion spots occur. In such sizing adhesion spots, especially in areas with a large amount of sizing, the threads are likely to stick, and when unwound in a higher-order processing step, fluff is generated due to sticking of the sizing agent, and finally the thread breaks. The problem arises.

In particular, when the number of yarns is increased in order to improve the productivity of carbon fibers, the spacing between the carbon fiber yarns becomes narrow, and the adjacent yarns easily come into contact with each other, which causes fuzz. Therefore, there is a problem that sizing adhesion spots increase and yarn breakage due to the adhesion spots increases. Further, since the space between the adjacent yarns is narrowed, a sizing liquid film is likely to be generated between the yarns, and if it is dried as it is, a new problem occurs that the sizing agent adheres unevenly.

With respect to the prevention of uneven adhesion of the sizing agent, Japanese Patent Application Laid-Open No. 59-36762 proposes to subject the yarn after applying the sizing agent to ultrasonic irradiation. However, in today's world where the number of yarns is increasing, there is a problem that performing ultrasonic irradiation treatment on each yarn increases equipment cost and manufacturing cost.

Further, Japanese Patent Application Laid-Open No. 59-36763 discloses a plurality of grooved rollers used when applying a sizing agent,
It is proposed to make two or more different shapes. However, in this method, fluff may be generated due to running of the grooved roller.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, that is, in the sizing treatment of carbon fiber, with relatively inexpensive equipment, fluffing of the sizing agent caused by fluff and The purpose is to reduce the adhesion unevenness of the sizing agent that is generated by the sizing liquid film at the time of multi-thread formation, and to prevent the occurrence of fluff or yarn breakage in the subsequent steps.

[0008]

The above object of the present invention is to apply a sizing agent to carbon fiber yarns by immersing the carbon fiber yarns in a sizing agent solution or dispersion, and then applying no pressurized gas. This can be achieved by a carbon fiber sizing method characterized by spraying at a flow rate of 0.5 to 10 m / sec.

The present invention will be specifically described below.

Usually, the carbon fiber yarn is dipped in the sizing agent solution, and then the applied sizing agent is dried. The feature of the sizing treatment of the present invention is that the carbon fiber yarn after the sizing agent is applied is blown with pressurized air. It is in. That is, according to the research conducted by the present inventors, the following facts have been found regarding the adhesion unevenness of the sizing agent in the sizing treatment of carbon fibers.

Since carbon fibers are essentially rigid and brittle as described above, fluff is already generated by contact with a roller or the like in the step before the sizing treatment step. When a sizing agent is applied to the fluffy yarn, the sizing adhesion amount at the fluffing portion locally increases, causing adhesion unevenness.

Further, recently, there is a remarkable tendency that the treated yarn density is increased for the purpose of improving the productivity, and the interval between the yarns becomes narrower as the adjacent yarns come into contact with each other. When the carbon fibers of multiple yarns are run at such a narrow interval that adjacent yarns come into contact with each other, fluffs are likely to occur due to contact between adjacent yarns, and even if fluffs do not occur, the surface tension of the sizing liquid adheres to them. A liquid film of the sizing liquid is generated between the adjacent yarns, and the amount of sizing adhered to that portion is increased to 2-3 times that in the normal state.

According to the present invention, in order to prevent excessive adhesion of a sizing agent caused by fluff existing in a carbon fiber yarn and to prevent the formation of a sizing liquid film between adjacent yarns, the yarn after applying the sizing agent is used. A pressurized gas is blown to reduce sizing adhesion spots. By blowing the pressurized gas, the excess sizing agent attached to the fluff portion of the yarn is uniformly removed, or by blowing the pressurized gas having a flow velocity higher than the surface tension of the sizing liquid between the adjacent yarns. Liquid film generation can be prevented.

In the present invention, the flow velocity of the pressurized gas refers to the actual flow velocity in the immediate vicinity of the treated yarn, and the flow velocity range at that time is 0.5 to 1.
It is 0 m / sec, preferably 1 to 5 m / sec. That is, when the gas flow rate is less than 0.5 m / sec, there is no effect of removing the excess sizing liquid and preventing the formation of a sizing liquid film. Further, if the flow velocity exceeds 10 m / sec, the fluff of the yarn may increase due to the flow velocity and yarn breakage may occur.

Further, the tension of the yarn during the sizing treatment is from 0.05 to 100 per single fiber from the viewpoint of preventing the generation of fluff due to vibration and fluctuation of the yarn and the prevention of fluff due to excessive tension.
1.0 g is preferable, but not particularly limited.

The carbon fibers in the present invention are so-called carbonized yarns and graphite yarns obtained by a known method using various fibers such as acrylic, pitch and cellulose fibers as precursors, and those obtained by surface oxidation treatment of these. Is included.

The sizing agent is used as an aqueous solution and / or an aqueous dispersion, or an organic solvent solution, which imparts a sizing property to the carbon fibers, improves the bending resistance and the abrasion resistance, and A sizing agent that can obtain good composite material properties when the carbon fiber is used as a reinforcing fiber of the composite material is preferably used, but in particular,
In the case of an aqueous solution and / or an aqueous dispersion system, the generation of a liquid film due to the above-mentioned surface tension is remarkable and the effect is large. To the sizing agent used as an aqueous solution and / or an aqueous dispersion, for example, a polyalkylene oxide and its derivative, polyvinylpyrrolidone and its derivative, a water-soluble resin such as polyvinyl alcohol, or various surfactants may be added to disperse the water. Various known resins such as an epoxy resin and an unsaturated polyester resin that can be used are listed, but are not particularly limited to the above resins. In addition, you may mix | blend 2 or more types of these sizing agents.

As the sizing agent used as the organic solvent solution, for example, glycidyl ether type, glycidyl ester type, glycidyl amine type, aliphatic epoxide type epoxy resin, unsaturated polyester resin, polyamide resin, polyimide resin and the like are known. Various resins are listed.

The organic solvent in which these sizing agents are dissolved may be any solvent which can dissolve the above resins in a stable manner, and examples thereof include aromatic hydrocarbons such as benzene, toluene and xylene, ketones such as acetone and methyl ethyl ketone, and the like. Examples thereof include halogenated hydrocarbons such as carbon tetrachloride, trichlene, and chloroform, and modified ethers such as cellosolve, but are not particularly limited to the above resins. It may be appropriately selected depending on the boiling point and industrial handling. Two or more kinds of organic solvent-based sizing agents may be blended.

The aqueous solution, aqueous dispersion or organic solvent solution of the sizing agent may be prepared by a conventionally known method according to the characteristics of the sizing agent, provided that the bath concentration of the sizing agent is usually 0.5 to 10% by weight. Ranges are preferably used.
The amount of the sizing agent attached to the carbon fibers varies somewhat depending on the type of the sizing agent, but is generally in the range of 0.2 to 5% by weight per carbon fiber.

[0021]

EXAMPLES The present invention will be specifically described below with reference to examples. The number of fluffs and the number of yarn breaks in this example were determined by the following methods.

(1) Number of fluff A carbon fiber yarn was subjected to a tension of 0.09 g per denier,
It is run at a yarn speed of 3 m / min, laser light is emitted from the side surface at a right angle to the fiber yarn, and the number of fluffs is detected by the fluff detection device and displayed in pieces / m.

(2) Number of yarn breakages The number of yarn breakages per 50 yarns when unwinding a bobbin of a carbon fiber yarn wound up by a normal method at a speed of 50 m / min by a vertical winding method was expressed.

[0024]

Example 1 Fifty untwisted acrylic carbon fiber yarns having a single fiber fineness of 0.6d and a number of filaments of 12,000 were used, a speed of 10 m / min, and a tension of the yarn was 0.2 g per single fiber. Using the sizing tank shown in Fig. 1 under the conditions of No. 1 and applying the sizing agent, the flow velocity is changed within the range of 0.5 to 10 m / sec from the hole with a diameter of several mm from the pipe several cm away from the yarn. The ambient temperature air was blown onto the carbon fiber yarn for about 0.5 seconds and wound up in the usual manner.

Among the 50 carbon fiber yarns thus obtained, the variation in the amount of sizing agent adhered within the same yarn (CV
Table 1 shows the values), the variation in the amount of the sizing agent adhered between the 50 yarns (CV value), and the yarn breakage state during unwinding. As the sizing solution, an aqueous emulsion solution containing 4% resin was used, and the amount of the sizing agent attached was 1.2% based on the weight of carbon fiber.

[0026]

[Comparative Example 1] A carbon fiber yarn was wound in the same manner as described in Example 1 except that the flow rates of normal temperature air were changed to 0, 0.3 and 12 m / sec. The 50 carbon fiber yarns thus obtained have the same sizing agent adhesion amount variation (CV) within the same yarn.
Table 1 shows the values), the variation in the amount of the sizing agent adhered between the 50 yarns (CV value), and the yarn breakage state during unwinding. If the flow velocity is less than 0.5 m / sec, the CV value of sizing adhesion is high, and fluff and yarn breakage increase. The flow velocity is 10m /
It can be seen that fluff and yarn breakage increase when the time is exceeded.

[0027]

[Table 1]

[0028]

INDUSTRIAL APPLICABILITY In the sizing treatment of a carbon fiber yarn, the present invention is generated by the fluff contained in the carbon fiber yarn by a completely new means of blowing a pressurized gas to the yarn after applying the sizing agent. The excessive deposition of the sizing agent or the surface tension of the sizing liquid significantly suppresses the generation of the sizing liquid film between the adjacent yarns. Therefore, the adhesion unevenness of the sizing agent on the carbon fibers is significantly reduced, and it is possible to prevent the occurrence of fluff and yarn breakage in the following steps, which is a remarkable effect in the production of carbon fibers.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an example of a sizing treatment facility according to the present invention.

[Explanation of symbols]

 1: Roller 2: Treated yarn 3: Sizing liquid 4: Pressurized gas supply pipe 5: Pressurized gas (air)

Claims (1)

[Claims] 1. When applying a sizing agent to a carbon fiber yarn, the pressurized gas is blown at a flow rate of 0.5 to 10 m / sec after the carbon fiber yarn is immersed in a sizing agent solution or dispersion. A method for imparting sizing of carbon fiber, comprising: