JPH0351319A - Treating agent for pitch-based carbon fiber - Google Patents

Abstract

PURPOSE:To obtain the title treating agent for using in a production process of a pitch-based carbon fiber capable of industrially advantageously and stably producing a fiber having good arrangement of fiber and high strand strength in simple operation by emulsifying a specific silicone oil with a fatty acid amine salt in water. CONSTITUTION:0.1-20% fatty acid amine salt expressed by formula II (R<1> is 5-14C alkyl; R<2>, R<3> and R<4> are <=4C alkyl or formula II) is added to a silicone oil (e.g. dimethylpolysiloxane) having 2-20cst viscosity at 25 deg.C and the silicone oil is dispersed in water to provide the aimed treating agent. Furthermore, when solid fine grains of graphite, silica, etc., having 0.01-5mu average grain size are dispersed into the treating agent and blended with the treating agent, effects on fusion among fibers is preferably increased.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention facilitates the handling of fibers when producing carbon fibers from pitches such as coal-based pitch, petroleum-based pitch, and fired polymer pitch. This invention relates to a pinch-type carbon fiber processing agent used in the process of manufacturing high-quality carbon fibers without adhesion or fusion between fibers.

(Prior Art) Pitch-based carbon fibers are usually produced by melt-spinning raw material pitch and subjecting the resulting pitch fibers to infusibility treatment and carbonization treatment.

Pitch-based carbon fiber is polyacrylonitrile (PAN)
Although pitch fibers have the advantage of being industrially advantageous and can be produced in higher yields than other carbon fibers, pitch fibers are extremely fragile and difficult to handle during infusibility and carbonization treatments. It is easy to cause fuzzing, wrapping around the guide roller, thread breakage, etc. Furthermore, during the infusibility treatment and carbonization treatment, adhesion or fusion between fibers occurs, and the obtained carbon fibers are easily damaged.

Therefore, we investigated various methods for stably producing high-quality pitch-based carbon fibers by solving the problems peculiar to pinch-based carbon fibers. Kaisho 60-2468
19) and the method using a silicone oil water emulsion (Japanese Patent Application Laid-Open No. 61-70017),
Although a patent application has already been filed, these processing agents were able to solve problems such as fuzzing of the fibers, winding around guide rollers, and yarn breakage during the spinning and convergence process, but they did not work properly in an oxidizing atmosphere at about 00°C. - Sufficiently eliminates fusion and adhesion between fibers during infusibility treatment performed in a heating zone of approximately 300°C or carbonization treatment performed at least at 400°C or higher in an inert atmosphere following such infusibility treatment. There was still room for improvement.

It has been found that the cause of such a phenomenon of fusion or adhesion is that some of the components contained in the processing agent decompose or turn into tar during heat treatment such as infusibility treatment or carbonization treatment.

Therefore, in order to solve this problem, silicone oil with a viscosity of 2 to 20 cst, which is hot at 25°C, was heated to 300°C.
A processing agent emulsified in water with a surfactant that has a heating residual amount of 5% or less at 30 to 350°C and has virtually no exothermic peak in the differential exothermic curve (DTA) at 30 to 350°C (JP-A-64 -26720) was proposed.

(Problems to be Solved by the Invention) However, although such treatment agents can sufficiently improve adhesion or fusion between fibers, the problem is that the strand strength of the fibers in the final product form is not sufficiently improved. was left behind.

(Means for Solving the Problems) Therefore, the present inventors conducted intensive studies to solve these problems, and as a result, they found that the treatment agent used in the pitch-based carbon fiber manufacturing process was Viscosity 2~20cst
We have discovered that the strand strength of the final fiber can be significantly improved by using a silicone oil emulsified in water with a specific fatty acid amine salt, and have solved the conventional problems and arrived at the present invention. That is, the purpose of the present invention is to solve not only problems such as fuzzing of fibers, sticking to rollers, and yarn breakage when producing pinch carbon fibers, but also problems such as fusion and adhesion between fibers during heat treatment. The purpose of the present invention is to provide a process treatment agent that can eliminate the above problems and stably produce pitch-based carbon fibers with good thread alignment and high strand strength.

The object of the invention is to provide a processing agent used in the process of producing pinch-type carbon fibers, wherein the processing agent is a silicone oil having a viscosity of 2 to 2 (lc st) at 25° C. according to the following general formula (1). A treatment agent for pitch-based carbon fibers characterized by being an emulsified state of a fatty acid amine salt in water (wherein 1 represents an alkyl group having 5 to 14 carbon atoms, and R'1 .R3 and R4 represent an alkyl group having 4 or less carbon atoms or a -CtHsOH group, which may be different from each other.).

The present invention will be explained in detail below. The raw material pitch used in the present invention includes coal tar pinch, coal-based pitch such as coal liquefied product, atmospheric distillation residue of crude oil, vacuum distillation residue, or heat-treated products thereof, and heat treatment of naphtha pyrolysis byproduct tar. Examples thereof include petroleum-based pitch such as synthetic resin and calcined polymer pitch obtained by carbonizing synthetic resin or natural resin.

Melt spinning of raw material pitch can be carried out by extruding it into the gas phase through a spinneret in the same manner as melt spinning of polyester and polyamide. Preferably, a method is employed in which the pitch is melted using an extruder or the like, extruded through a downward spinneret into the gas phase, and then cooled and solidified. The spinneret is one with a discharge hole diameter of about 0.1 to 0.3 mm.
Use. The temperature of the spinneret depends on the type of raw material pitch and is determined in consideration of the melt viscosity suitable for spinning, but it is usually within the range of 250 to 350°C. Providing a heat insulating cylinder under the spinneret is effective in stabilizing the spinning state.

The present invention is a treatment agent prepared by dispersing silicone oil in water using a surfactant to adhere to the pinched fibers obtained by the above method or the fibers treated to make it infusible. 20cst (25℃)
It is important to use dimethylpolysiloxane or various modified polysiloxanes. Here 2 cst (25
If the treatment agent is less than 20 cst (°C), it is undesirable because it is highly volatile, so the treatment agent will volatilize after being attached to the carbon fiber, and it will not have sufficient effect as a treatment agent.
If the temperature is higher than 25°C, it is not preferable because it causes fusion of carbon fiber single filaments during infusibility or carbonization, resulting in deterioration of fiber properties.

Specific examples of such silicone oils include dimethylpolysiloxane, methylphenylpolysiloxane, and hydrogenpolysiloxane, but
In addition, those modified with one or more of alkyl groups such as epoxy groups, ethyl and propyl groups, amine groups, carboxyl groups, alcohols, phenyl groups, and polyether groups are used. Moreover, these silicone oils may be used alone or in a mixture of two or more thereof.

The surfactant that emulsifies the silicone oil is as follows:
A fatty acid amine salt represented by the following general formula (1) is used.

In the formula, RI=alkyl group having 5 to 14 carbon atoms, R2, R:
l, R4 = alkyl group having 4 or less carbon atoms or -C2H
s Represents an OH group, and these may be the same or different.

Preferably, R1 is a higher alkyl group having 8 to 14 carbon atoms,
At least one of R1, R, 3, and R4 is -C2Hs
It is preferably an OH group, and the other is an alkyl group with a small number of carbon atoms such as a methyl or ethyl group.

Specifically, lauric acid dimethylethanolamine salt or myristic acid dimethylethanolamine salt is preferred.

The above surfactant is preferably used in an amount of 0.1% to 20% based on the silicone oil. If it is less than 0.1%, no emulsion of silicone oil will be formed, and if it is more than 20%, it will have an adverse effect on the carbon fiber properties after heat treatment such as infusibility.

Further, it is preferable to disperse and mix solid fine particles into the treatment agent of the present invention, since this increases the effect of preventing adhesion or fusion between fibers.

As solid particles, carbonaceous particles, inorganic oxide particles, inorganic salt particles, or mixtures thereof are preferably used, and specifically, graphite, carbon black, silica, calcium carbonate, titanium oxide, talc, clay,
Fine particles of barium sulfate, potassium titanate, molybdenum disulfide, and the like are used, and among them, graphite, carbon black, warping force, and calcium carbonate are preferably used. In order to preferably infiltrate these particles between the pinch fibers, the average particle diameter is 15 μm or less, preferably 0°01 to 5 μm.
A size of μ, more preferably 0.05 to 3 μ is used.

Graphite can be either natural or synthetic. Carbon black obtained by various methods such as furnace blank, thermal black, lump black, and contact blank can be used. As the silica, fine silica particles called fumed silica or white carbon, which are obtained by a dry method or a wet method such as thermal decomposition of silicon halide or acid decomposition of sodium silicate, are used. As the calcium carbonate, ultrafine precipitated calcium carbonate, colloidal calcium carbonate, and activated calcium carbonate obtained by mechanically crushing limestone or treating it with a chemical precipitation method are used.

Talc, clay, titanium oxide, barium sulfate, potassium titanate, and molybdenum disulfide are commercially available as fillers for plastics, rubber, etc., and those having the above-mentioned particle size are used.

Methods for attaching the treatment agent to the fibers include a method of spraying, a method of applying the treatment agent to the fibers, and a method of bringing the treatment agent into contact with the fibers, a method of immersing the fibers, and the like.

The amount of the treatment agent deposited is preferably 0.02% to 15% by weight in terms of oil content.

If it is less than 0.02% by weight, the fiber cohesiveness will be poor, and if it is more than 15% by weight, it will adversely affect the outer shape of the fiber after infusibility.

The pitch fibers to which the treatment agent has been attached and bundled are subjected to infusibility treatment and carbonization treatment according to well-known methods. For example, the infusibility treatment is carried out by subjecting the fibers to 150%
This is done by heating to a temperature of ~360°C for 5 minutes to 10 hours.

Moreover, the treatment agent can also be used as a process oil for carbon fibers after infusibility. Carbonization treatment involves heating the fibers to a temperature of 400 to 2500°C in an inert gas atmosphere such as nitrogen or argon.
．． This is done by heating for 5 minutes to 10 hours.

When further graphitizing treatment is performed, 2500 to 350
What is necessary is just to heat and hold at the temperature of 0 degreeC for about 1 second to 1 hour. Furthermore, during the infusibility, carbonization, or graphitization treatment, a slight load or tension may be applied to the object to be treated, if necessary, in order to prevent shrinkage, deformation, etc.

The carbon fibers or graphite fibers obtained in this way are usually used for their respective purposes after being defibrated.

(Examples) Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist thereof is exceeded.

Examples 1 to 3 Tar-based raw material pitch was melt-spun into the gas phase at a preventive spindle temperature of 330°C, and the resulting pitch fibers with a yarn diameter of 10μ and 120 filaments were coated with the treatment agent shown in Table 1 using an oiling guide. The bundled fibers were then dried by holding them at 80°C for 30 minutes in the air.Then, the temperature was raised from 150°C to 350°C over a period of 2 hours and 40 minutes, and then the temperature was increased to 350°C. The mixture was held for 30 minutes to perform infusibility treatment. After that, the temperature was raised from room temperature to 1400°C in argon over 2 hours and 20 minutes, and then maintained at that temperature for 1 hour to carry out carbonization treatment.
to 2500℃ in 1 hour 15 minutes, 90ml
A graphitized thread was obtained.

The bundled state of threads, the properties of infusible fibers, the fused state of single threads, and the strength of graphitized thread strands during the carbon fiber manufacturing process were measured. The results are listed in Table 1.

Comparative Examples 1 to 4 The results were carried out in the same manner as in Example 1 by changing the type of sizing agent.
Shown in the table.

From the results in Table 1, it is clear that the processing agent according to the present invention has excellent performance.

(Effects of the invention) By using the treatment agent for pitch-based carbon fibers of the present invention, which is prepared by dispersing silicone oil having specific physical properties in water with a surfactant having specific physical properties, brittle fibers can be treated with a simple operation. At the same time, it is possible to easily handle the fibers, prevent adhesion or fusion between the fibers, and produce pitch-based carbon fibers with good strand strength in the form of continuous filaments under industrially advantageous conditions.

Claims (2)

[Claims] (1) A processing agent used in the process of producing pitch-based carbon fiber, wherein the processing agent has a viscosity of 2 to 20 cs at 25°C.
1. A treatment agent for pitch-based carbon fibers, which is obtained by emulsifying a silicone oil of t in water with a fatty acid amine salt represented by the following general formula (I). ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, R^1 represents an alkyl group having 5 to 14 carbon atoms, and R^2, R^3, and R^4 represent an alkyl group having 4 or less carbon atoms. represents an alkyl group or a -C_2H_5OH group, which may be different from each other.) (2) Claim 1 in which the amount of surfactant added to the silicone oil in the processing agent is 0.1% to 20wt%.
Treatment agent as described.