JPS61119717A - Bundle of water-absorbing carbon fiber of high performance - Google Patents

Abstract

PURPOSE:The titled carbon fiber bundle that has a specific saturated water content, a strand strength and elasticity, thus being suitable for production of reinforced tire cords to which RFL is applied, reinforced paper and reinforced cement, because it has high affinity to water and high strength and elasticity. CONSTITUTION:The objective carbon fiber bundle has a carbon content of 70-90wt%, a saturated water content of at least 0.5wt% at 80% RH and 20 deg.C, a strand strength of 250kgf/mm<2> and a strand elasticity of more than 18,000kgf/ mm<2>. The fiber bundle is preferably produced from acrylic fibers containing more than 95wt% acrylonitrile.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to a carbonaceous fiber bundle that can be obtained by low-temperature firing and has a high affinity for water, high strand strength, and high strand elastic modulus. This product is manufactured using water and processed through kneading, such as RFL.
It is suitably used in the production of tire cords, paper, and cement-reinforced mats to which (resorcinol-formalin latex) is attached.

(Background Art) In recent years, carbon fibers with a carbon content of 95% by weight or more have high strength and high elastic modulus, and have a specific gravity of 1.6 to 1.9.
In the form of fiber bundles (strands) or chops, 8-layer 71 helix materials, such as thermosetting or thermoplastic plastics, are composited and are widely used mainly in the fields of aircraft, automobiles, and sporting goods.

However, carbon fibers, which are usually manufactured using acrylic fibers as precursors, suffer from a weight loss of 45 to 50% during carbonization, and in addition, the firing temperature is 1000°C or higher, which increases the cost of raw materials. , higher energy costs,■
Since it requires a high-temperature furnace of 1000° C. or higher and special high-temperature heat-resistant materials used in it, the equipment cost is also high, making it an expensive product. Although carbon fiber is expensive, it is a material with excellent physical properties, so it is widely used in industrial fields where quality is a priority. tended not to be used frequently.

In particular, the carbon iI group has a saturated moisture content of 0.1% by weight or less at a relative humidity of 80% and a temperature of 20°C, and has insufficient affinity with water. When using carbon fiber as a rubber reinforcing material when making a tire cord using a dispersion liquid,
RFL has poor impregnability between fibers and insufficient adhesion, resulting in low strength as a cord.

On the other hand, some fibers with a carbon content of 90% by weight or less (referred to as carbonaceous I! string), which is an intermediate stage in the production of carbon fibers, have an affinity for water, and these fibers have physical properties. It is inherently more advantageous than carbon fiber in terms of both cost and cost. Nevertheless, the fiber assembly performance of conventional carbon fibers is significantly lower than that of carbon fibers, so even if the cost of 1 meter of carbon fiber is low, carbon fibers are more advantageous than carbon fibers. The use of quality fibers was low. However, if the performance of this carbonaceous m-fiber can be improved, carbonaceous l1r4tt will become extremely useful, especially as a tire cord, and its use is expected to expand.

(Problem of the Invention) The present inventors have solved the above-mentioned drawbacks of carbonaceous fibers, and as a result of studying fibers that have a high affinity for water and a high elastic modulus comparable to carbon fibers, This led to the present invention.

In particular, the object of the present invention is to provide RF for rubber reinforcement 1. - (Resorcin formalin latex) A carbon fiber bundle suitable as a cord for adhesion is provided.

(Structure and operation of the invention) The present invention has a carbon content of 70 to 90% by weight, a saturated moisture content of at least 0.5% by weight at a relative humidity of 80% and a temperature of 20°C, and strand strength. 250kg
f/mm' or more, strand elastic modulus 18000kQf
/mm' or more.

Conventionally known carbon W! Navy blue has a carbon content of more than 95% by weight, but the fiber bundle of the present invention has a carbon content of
The flame resistance is much lower than that of carbon fiber and higher than that of the precursor (acrylic fiber), and in this respect it is a fiber that falls in the intermediate range between flame resistance and carbon fiber. Such a fiber bundle of the present invention has properties comparable to carbon fibers in strand strength and strand elastic modulus, and exhibits a hydrophilicity 5 to 50 times higher than that of carbon Il navy blue.

The carbon fiber bundle of the present invention has a relative humidity of 80% and a temperature of 20°C.
The saturated moisture content is at least 0.5% by weight.

If the amount is less than 0.5%, when the fiber bundle is immersed in an aqueous dispersion of RFL to attach RFL, the mono[
This is undesirable because the resulting RFI-attached cord has a cord strength considerably lower than that obtained from the original strand strength because the RFL is not sufficiently impregnated during the stranding process and the RFL and the fibers are not strongly bonded.

The carbonaceous 11i 1ft bundle of the present invention has a strand strength of 25
0kgf/mm' or more, strand elastic modulus 18000
kof/mm2 or more. If the strand strength is less than 250k (If/l11m'), the strength of the RFL-attached cord is low, so the strength of the RFL-attached cord is inferior to that of the conventionally known RFI-attached carbon fiber, and other Since it is inferior to a cord made of glass fiber or an aramid fiber cord, it is not preferable because the practical merit I- is reduced.In addition, the strand elastic modulus is 18,000 kof/
If less than mm', the l! The cost performance of I-fibers in terms of the relationship between elastic modulus and cost is inferior to that of carbon fibers, so they are not preferable.

The carbonaceous mw11 bundle of the present invention has high strength as a rubber reinforcing cord and has excellent adhesiveness to rubber.
It is a new and useful textile material.

In the present invention, the moisture content of the carbon fiber bundle is a value measured as follows. The value is determined by the following formula when the moisture content is brought to equilibrium by being left standing at 20° C. for one week in a container with a relative humidity of 80% (prepared using a saturated ammonium chloride aqueous solution).

Weight of fiber after 1 week - 4I after drying at 105°C for 30 minutes
Fiber bundle weight moisture content - xloo (%) Fiber bundle weight after drying at 105° C. for 30 minutes The carbon content is a value measured with an elemental analyzer (manufactured by Yanagimoto Co., Ltd.). Strand strength and strand elastic modulus are
This is a value measured according to J I 5R7601.

Such a carbon fiber bundle of the present invention can be obtained using acrylic fibers as a precursor.

A preferred example of the method for producing the carbonaceous fiber bundle of the present invention will be described.

An acrylic fiber containing 93% by weight or more of acrylonitrile is used as a precursor in a flameproofing furnace at 200 to 300°C in air to make it flameproof, and then heated to 750℃ in an inert gas.
Calculate at ~1000°C.

In particular, in order to obtain fibers having the strand strength and strand elastic modulus specified in the present invention, the molecular orientation of the fibers should be increased during flame resistance, the flame resistance should be uniform, and the tension during firing should be set to a high <L , f It is desirable to adjust the specific gravity of the four flame-resistant fibers to correspond to the tension during firing. Further, in order to coat the fibers with a moisture content of at least 0.5% by weight, particularly 0.5 to 5% by weight as defined in the present invention, it is preferable to adjust the firing humidity and firing time.

Below, a specific example will be shown and a more detailed explanation will be given of the method of preparing 1 q of carbon fiber bundles of the present invention.

The acrylic fiber was obtained by copolymerizing 93% by weight or more of acrylonitrile with a known comonomer [
1, and in particular, as a comonomer, methyl acrylate 1
~5%, sodium methallylsulfonate 0.1~0.5
% by weight or a component selected from 0.5% to 1.5% by weight of itaconic acid with a molecular weight of 30,000 to 1oooo
o Molecular orientation degree 85% or more, single fiber denier 0.1-1.
A bundle of m strings of 0.100 to 100,000 is preferred.

Flameproofing: The acrylic fiber bundle is heated in an oxidizing atmosphere, mainly in the air, in a flameproofing furnace equipped with a group of multi-stage rollers while gradually increasing the temperature at a temperature 10 to 60°C lower than the decomposition temperature of the fibers. , the specific gravity of the fibers is reduced to 1.
33. ~1.40.

In particular, in order to obtain the 1ift bundle of the present invention, tension and temperature are applied to make the acrylic fibers flame resistant so that the degree of orientation of the acrylic fibers at an X-ray diffraction angle of 2θ-176 is maintained at 80% or more when made into flame resistant fibers. More preferably, the acrylic fibers having a degree of orientation of 20-116 of 88% or more are made flame resistant under a tension of 100 to 2001 g/d.

When the tension is less than 100111 (1/d), the elastic modulus of the obtained carbon fiber bundle is low;
If it exceeds /d, the carbonaceous m string bundle will have an extremely large amount of fuzz, which tends to cause problems in terms of the required quality of the bundle.

Regarding the flame resistance temperature, it is appropriate to increase the temperature in stages so that the reaction between the fiber and oxygen associated with flame resistance and the cyclization reaction of the nitrile groups in the fiber occur uniformly on the cross section of the fiber. It is. Preferably, the temperature is started at a temperature 10 to 60°C lower than the decomposition temperature of the acrylic fiber in air, and the temperature is raised stepwise to a temperature 2O-9 = -30°C lower than the decomposition temperature.

It is appropriate that the flameproofing time is 0.3 to 1 hour so that the specific gravity of the flameproof cloth is 1.33 to 1.40. When the specific gravity of the flame-resistant fiber is less than 1.33, it is not preferable because the weight percent (carbonization rate) of the obtained carbonaceous fiber to the number of precursor fibers becomes extremely small. Moreover, when the ratio exceeds 1.40, the strength of the obtained carbonaceous fiber tends to decrease.

An example of a flameproofing furnace used to obtain the fiber bundle of the present invention is a furnace having a group of multistage rollers as shown in FIG. It has a structure in which the fibers can be adjusted, and the fibers are continuously supplied into the furnace from the supply roller Rrp, made flame resistant, and finally taken off by the roller Rtp.

Fire-resistant fibers are fired in an atmosphere of nitrogen, argon, etc.
The process is carried out at a temperature of 50° C. to 1000° C., and is usually carried out by continuously passing the fiber through a furnace as shown in FIG.

-10= If the firing temperature is less than 750°C, the moisture content tends to increase, but the strand strength and strand elastic modulus decrease, which is not preferable. Further, if the temperature exceeds 1000°C, the fiber will have a moisture content of less than 0.5% by weight, which is not preferable. The firing time depends on the temperature, and is preferably shortened when the temperature is high, but 0.5 to 10 minutes is usually appropriate.

If the time is less than 0.5 minutes, 11 fibers with high moisture content can be used.
The strand elastic modulus tends to decrease.

If it takes more than 10 minutes, energy costs tend to increase.

In particular, in order to obtain #JAIf# of the present invention, the tension must be set at 150+119/d to 250111g/d during firing.
It is preferable to multiply by d. In the case of 150 mg/cl without vortex, the strand strength and strand elastic modulus are low, and
If it exceeds 250 mg/d, the fibers produced by 1 q of fiber tend to have a lot of fuzz, resulting in poor quality fibers.

Normally, when the specific gravity of the flame-resistant fiber is 1.33 to 1.40, it is desirable that the tension during firing is 150 to 250 mg/d, and the tension is increased according to the specific gravity of the flame-resistant fiber.

FIG. 2 shows the supply roller RfC, the furnace core tube 2, the furnace body 3,
A firing furnace composed of a heat insulating material 4, a heater 5, and a take-up roller Rtc, in which the fiber 1 is
Continuously passing through the furnace core cylinder through the roller Rt
It is fired in such a way that it is removed at c.

(Effects of the Invention) The carbon fiber bundle of the present invention has excellent affinity with water, strength,
Because of its high modulus and performance comparable to carbon fiber, it is useful for making tire cords that are fully impregnated with RFI- and exhibit high cord strength.

Furthermore, the product of the present invention is used in the production of products that are produced using water as a medium. For example, it is effective when making paper and covering it with paper, or when mixing it with cement to strengthen it. Furthermore, since the material of the present invention has performance comparable to carbon fiber, it is useful as a reinforcing material for plastics.

(Example and comparative example) The present invention will be explained in more detail by giving examples.

At the same time, comparative examples are also given. Unless otherwise specified, "%"
"Parts" are expressed by weight.

The degree of orientation in X-ray diffraction is determined by the diffraction angle 2θ-17° or 2
This is a value determined from the following using the orientation angle φ at θ-25° and the half width W1/2 of the diagram of the diffraction intensity.

90-W 1/2
Pages 75-383] The procedure was carried out using the method in the appendix.

Example 1.2 and Comparative Example 1 A polymer consisting of 96% acrylonitrile, 1% itaconic acid, and 3% methyl acrylate (ratio L 65000), the degree of orientation at 2θ-17° was 88%, and the air Acrylic fiber navy blue bundle (single fiber navy blue) with a decomposition temperature of 287°C.
8 denier, 12,000 pieces) were passed through a supply roller Rfp to the flameproofing furnace shown in Fig. 1, and the furnace temperature was 25.
1st zone at 0℃ for 30 minutes and furnace temperature at 263℃ for 24 minutes.
In the second zone for 1 minute, the sample was continuously taken off with a take-off roller (Rtl).

During flameproofing, the tension applied to w4#1 in a portion of each roller was 105 mg/d, and the degree of X-ray orientation at 2θ-17° of the flame-resistant fiber finally obtained was 81%. Furthermore, the fibers in the same roller portion were observed with an optical microscope, and it was confirmed that the degree of development of the black portion in the cross section of the fibers was uniform, and that the flame resistance reaction was occurring uniformly.

The specific gravity of the obtained flame-resistant fiber bundle was 1.35.

This flame-resistant fiber bundle was put into the oven at a temperature of 330°C and a maximum temperature of 93°C in the furnace.
It was introduced into the firing furnace shown in FIG. 2 at 0° C., and taken off with a take-off roller RtC for 3 minutes at the maximum temperature.

The tension during firing was set at 30 m0/d between the supply roller RfC and the take-up roller Rtc (Comparative Example 1), 18
0mo/d (Example 2), 240mg/d
(Example 1) Three types of carbon fiber bundles were obtained. The moisture content, strand strength, and strand elastic modulus of the obtained carbon fiber bundle were as shown in Table 1.

These three types of carbon fiber bundles were each mixed at 20% RFL (
Resorcin formalin latex) (Resorcin 8.5
A mixture of 4.1 parts of formalin (37% aqueous solution), 15 parts of vinylpyridine, 15 parts of styrene, and 62.6 parts of terpolymer rubber latex consisting of 70 parts of butadiene and aged at 20°C for 7 days. ]After being continuously immersed in an aqueous dispersion and pulled up, dried at 125℃ for 3 minutes,
Heat-treated at 20℃ for 1 minute to remove the RFL-attached cord (q).

Regarding the obtained 3fI type code, the attached RF I'L
When the ratio of cord strength to cord strength and strand strength was determined, the results shown in Table 1 were obtained.

As shown in Table 1, the carbon fiber bundles obtained in Examples 1 and 2, in which the tension during firing was increased, satisfied the specified values of the present invention in terms of moisture content, strand strength, and strand property. Showing excellent candy, the RFI-processing code also
The FL was sufficiently attached, and the ratio of the cord strength to the strand strength calculated from the strand strength by measuring rod strength also showed a high value.

On the other hand, the fiber obtained in Comparative Example 1, in which the tension during firing was lowered, had a particularly low S-herand modulus and was of little practical merit.

Comparative Example 2 The temperature inside the flameproofing furnace was set to 265°C (22°C lower than the decomposition temperature of the acrylic fiber to be treated), and the specific gravity was 1.3
Carbonaceous fibers were obtained in the same manner as in Example 1, except that the flame-resistant fibers of No. 5 were used.

1 m of the obtained carbonaceous material had a carbon content of 83% and a moisture content of 3.
1%, the strand strength was 230 kgf/mm2, the strand elastic modulus was 20600 kOf/ml', and the strength was low mH. In addition, when RFL treatment was performed in the same manner as in Example 1, RF L (1 wear was 23%,
The strength of the cord is 60kg, which is quite low.

Examples 3 and 4 and Comparative Examples 3 and 4 Flame-resistant M fibers were heated to maximum temperatures in the furnace of 650°C, 760°C, and 850°C.
Four types of carbonaceous fibers were prepared in the same manner as in Example 1, except that the fibers were fired at four levels: , 1100°C.

Table 2 shows the performance of the 1q carbon fiber bundle, the amount of RFI-attached cord attached (processed in the same manner as in Example 1), cord strength, and the ratio of cord strength to strand strength.

According to this, the fiber bundle of Comparative Example 4 with a low moisture content is
I- does not impregnate the navy blue fiber, has a low bonding distance, has low cord strength, and has a low ratio of cord strength to strand strength, resulting in poor adhesion between RFL and gi navy blue.

The fiber bundle of Comparative Example 3 has low strand strength and strand elastic modulus. On the other hand, the fiber bundles of Examples 3 and 4 satisfied the specified values of the present invention and had excellent strand performance and cord RF L adhesion.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the flameproofing device, and FIG. 2 is a schematic diagram of the firing furnace. In the figure, each symbol is as follows. A: Flameproofing furnace first zone B: Flameproofing furnace second zone C: Flameproofing furnace partition wall Rfll, Rfc: Sole-F supply loaf -Rtp,
Rtc: respectively take-up roller 1: fiber, 2: furnace core tube,
3: Furnace body, 4: Heat insulating material, 5: Heater, 6: Seal material, 7: Inert gas supply port

Claims (2)

[Claims] (1) The carbon content is 70 to 90% by weight, the saturated moisture content at a relative humidity of 80% and a temperature of 20°C is at least 0.5% by weight, and the strand strength is 250kgf.
/mm^2 or more, strand elastic modulus 18000kgf/
A carbonaceous fiber bundle characterized by having a diameter of mm^2 or more. (2) The carbonaceous fiber bundle according to claim 1, which is obtained from acrylic fibers containing 93% by weight or more of acrylonitrile.