JP5524760B2 - Aramid fiber for rubber reinforcement, method for producing the same, rubber material - Google Patents

Description

  The present invention relates to an aramid fiber for rubber reinforcement, a method for producing the same, and a rubber material. More specifically, the present invention relates to an aramid fiber containing carbon black having excellent rubber adhesion, a method for producing the same, and a rubber material using the fiber as a reinforcing material.

  Conventionally, aramid fibers (totally aromatic polyamide fibers) composed of an aromatic dicarboxylic acid component and an aromatic diamine component, especially para-based aramid fibers, are made of rubber by taking advantage of their properties such as strength, high elastic modulus, and high heat resistance. It is suitably used for reinforcement.

  On the other hand, as aramid fiber, there are polyparaphenylene terephthalamide (PPTA) fiber and copolyparaphenylene 3,4'-oxydiphenylene terephthalamide fiber, and these fibers have many advantages, but are bonded to rubber. Due to the poor nature, it was difficult to make higher performance rubber materials.

In order to solve such problems, fibers imparted with adhesiveness have been considered. For example, a method of coating the fiber surface with an adhesive layer (for example, Patent Document 1: Japanese Patent Laid-Open No. 10-025667) has been proposed. ing.
However, the above method has a problem that although the adhesiveness with a high rubber is obtained, the coated adhesive layer is peeled off.

Japanese Patent Application Laid-Open No. 10-025667

  The present invention has been made against the background of the prior art, and an object thereof is to provide an aramid fiber excellent in rubber adhesiveness, a method for producing the aramid fiber, and a rubber material using the aramid fiber.

  The present inventor has intensively studied to solve the above problems. As a result, the present inventors have found that the above-described problems can be solved by containing carbon black and making it exposed to the fiber surface, and have completed the present invention.

That is, the present invention is an aramid fiber composed of an aramid polymer, the aramid fiber contains carbon black having an average particle size of 10 μm or less, and the ratio of the area of the carbon black to the total surface area of the aramid fiber is It is an aramid fiber for rubber reinforcement characterized by being 10 to 70%.
Further, the rubber material using the rubber reinforcing aramid fiber.

  Further, a spinning solution comprising an aramid polymer, carbon black having an average particle diameter of 10 μm or less of 3 to 50% by weight based on the weight of the aramid polymer, and a solvent is discharged from a nozzle, solidified in a coagulation bath, desolvated, and dried. To produce an aramid fiber in which the ratio of the area of carbon black to the total surface area of the aramid fiber is 10 to 70% by applying an abrasive to the aramid fiber and rubbing the aramid fiber. This is a method for producing aramid fibers for reinforcing rubber.

  The aramid fiber of the present invention contains carbon black, and after the yarn is formed, the carbon black is exposed to a large amount on the fiber surface by a method of applying an abrasive and contact heating and stretching with a heater. It is remarkably improved. For this reason, it can be used suitably for rubber materials.

Hereinafter, embodiments of the present invention will be described in detail.
<Aramid polymer>
The aramid polymer in the present invention can be obtained from low-temperature solution polymerization or interfacial polymerization of dicarboxylic acid dichloride and diamine in a solution.

[Raw material of aramid polymer]
(Diamine component)
Specific examples of the diamine component used in the present invention include p-phenylenediamine, 2-chloro p-phenylenediamine, 2,5-dichloro p-phenylenediamine, 2,6-dichloro p-phenylenediamine, and m-phenylene. Diamine, 3,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenyl sulfone, 3,3′-diaminodiphenyl sulfone, etc. alone or in combination It can be mentioned, but is not limited to these. Among these, as the diamine component, p-phenylenediamine, m-phenylenediamine, and 3,4'-diaminodiphenyl ether can be used alone or in combination of two or more.

(Aromatic dicarboxylic acid dichloride component)
Specific examples of the dicarboxylic acid chloride component used in the present invention include isophthalic acid chloride, terephthalic acid chloride, 2-chloroterephthalic acid chloride, 2,5-dichloroterephthalic acid chloride, and 2,6-dichloroterephthalic acid. Examples include, but are not limited to, chloride and 2,6-naphthalenedicarboxylic acid chloride. Of these, terephthalic acid dichloride and isophthalic acid dichloride are preferred as the dicarboxylic acid chloride component. Therefore, examples of the aramid polymer in the present invention include copolyparaphenylene 3,4'-oxydiphenylene terephthalamide, polyparaphenylene terephthalamide, and polymetaphenylene terephthalamide. Particularly preferred is copolyparaphenylene 3,4'-oxydiphenylene terephthalamide.

[solvent]
Further, as a solvent for polymerizing an aramid polymer, specifically, an organic polar amide solvent such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, Water-soluble ether compounds such as tetrahydrofuran and dioxane, water-soluble alcohol compounds such as methanol, ethanol and ethylene glycol, water-soluble ketone compounds such as acetone and methyl ethyl ketone, water-soluble nitrile compounds such as acetonitrile and propionitrile, etc. . These solvents can be used as a mixed solvent of two or more kinds, and are not particularly limited. The solvent is preferably dehydrated.
In this case, in order to increase the solubility, an appropriate amount of a generally known inorganic salt may be added before, during or after the polymerization. Examples of such inorganic salts include lithium chloride and calcium chloride.

[concentration]
The polymer concentration of the aramid solution used in the production of the aramid polymer of the present invention is preferably 0.5 to 30% by weight, more preferably 1 to 10% by weight. When the polymer concentration is less than 0.5% by weight, the entanglement of the polymer is small and the viscosity necessary for spinning cannot be obtained. On the other hand, when the polymer concentration exceeds 30% by weight, an unstable flow tends to occur when discharging from the nozzle, making it difficult to perform stable spinning.

(Composition of diamine component and aromatic dicarboxylic acid dichloride component)
Moreover, when manufacturing an aramid polymer, these diamine components and acid chloride components are preferably 0.90 to 1.10, more preferably 0.95 to 1.05 as a molar ratio of the diamine component to the acid chloride component. It is preferable to use.

[Others]
The end of this aramid polymer can also be sealed. In the case of sealing with an end-capping agent, examples of the end-capping agent include phthalic acid chloride and substituted products thereof, and examples of the amine component include aniline and substituted products thereof.
In the reaction of a generally used acid chloride and diamine, an aliphatic or aromatic amine or a quaternary ammonium salt can be used in combination in order to capture an acid such as hydrogen chloride formed.
After completion of the reaction, a basic inorganic compound such as sodium hydroxide, potassium hydroxide, calcium hydroxide, calcium oxide or the like is added as necessary to carry out a neutralization reaction.
The reaction conditions do not require special restrictions. The reaction between acid chloride and diamine is generally rapid, and the reaction temperature is, for example, -25 ° C to 100 ° C, preferably -10 ° C to 80 ° C.

  The aramid polymer thus obtained can be put into a non-solvent such as alcohol or water, precipitated, and taken out as a pulp. This can be dissolved again in another solvent and used for molding, but the solution obtained by the polymerization reaction can be used as it is as a molding solution. The solvent used for re-dissolving is not particularly limited as long as it dissolves the aramid polymer, but a solvent used for the polymerization of the aramid polymer is preferable.

(Carbon black)
The shape of the carbon black added to the aramid polymer is not particularly specified, but the average particle size is 10 μm or less, preferably 8 μm or less, particularly preferably 2 to 6 μm. When the average particle diameter exceeds 10 μm, yarn breakage occurs frequently during spinning, and continuous spinning is impossible.
Here, the average particle diameter is a value defined by a value measured by a particle size distribution meter.

(Carbon black content)
The content of carbon black in the aramid fiber is preferably in the range of 3 to 50% by weight and more preferably in the range of 5 to 20% by weight in view of spinning stability. When the content is lower than 3% by weight, the ratio of carbon black on the surface of the aramid fiber is reduced and it becomes difficult to obtain high adhesiveness. On the other hand, when the content exceeds 50% by weight, yarn breakage during spinning frequently occurs, and continuous spinning tends to be difficult.

(Carbon black surface area ratio)
In the present invention, it is important that the ratio of the surface area of the carbon black to the total surface area of the aramid fibers (hereinafter sometimes referred to as carbon black surface area ratio) is 10 to 70%, preferably 15 to 60%. . If the carbon black surface area ratio is less than 10%, the desired high rubber adhesion cannot be obtained. On the other hand, if it exceeds 70%, the polyamide fiber is spun and the yarn is easily broken in the hot drawing process described later, and the quality deteriorates. To do. As described above, with respect to the method of setting the carbon black surface area ratio to 10 to 70%, the aramid fiber is spun with 3 to 50% by weight of carbon black as described above, and dried as described in detail later. It can be easily achieved by applying an abrasive in a yarn state and rubbing.

In the present invention, the carbon black surface area ratio refers to the blackness of the fiber by irradiating with UV excitation light using an epi-illumination fluorescence microscope, capturing a digital image for a length of 20 cm in the fiber axis direction, and performing image processing. The area of each part is (b), the total surface area of the fiber is (S), each area is measured, and the carbon black surface area ratio is a value obtained from equation (1).
Carbon black surface area ratio = (b) / (S) × 100 (%) (1)

<Method for producing aramid fiber>
In the present invention, an aramid fiber is prepared by preparing a spinning solution (dope) comprising an aramid polymer, carbon black having an average particle size of 10 μm or less, and a solvent, and discharging the obtained dope from a nozzle to coagulate comprising a poor solvent. It can be produced by coagulation, desolvation in a bath, heat treatment (drying) and stretching.

In order to suppress the aggregation of the carbon black when blending the carbon black into the spinning dope, in the preparation of the spinning dope, the carbon black dispersion is injected into the aramid polymer solution at a constant pressure, and dynamic mixing and A method of static mixing is preferred.
The polymer concentration of the dope for spinning, that is, the concentration of the aramid polymer is preferably 0.05 to 30% by weight, more preferably 1 to 10% by weight.

  The spinning dope in the present invention includes other components within the range not impairing the effects of the present invention, such as an antioxidant, a heat stabilizer, a weathering agent, a dye, an antistatic agent, a flame retardant, a conductive polymer, and the like. The polymer can be added.

  The spinning dope is discharged from a nozzle by a wet method, a semi-dry semi-wet method, etc., solidified in a coagulation bath, desolvated, and dried to obtain a fibrous material. Subsequently, the fibrous material made of the aramid polymer is stretched under heating conditions. The draw ratio is preferably in the range of 2 to 10 times, more preferably 3 to 6 times in view of mechanical properties. When the draw ratio is lower than 2, it is difficult to obtain the characteristics of an aramid fiber as a high strength fiber. On the other hand, when the draw ratio exceeds 10 times, yarn breakage during drawing frequently occurs and continuous drawing becomes difficult. The stretching temperature is preferably 450 to 550 ° C., more preferably 500 to 530 ° C., in view of mechanical properties. When the stretching temperature is lower than 450 ° C., yarn breakage during stretching frequently occurs and continuous stretching tends to be difficult. On the other hand, when the stretching temperature exceeds 550 ° C., thermal degradation of the aramid polymer occurs, and it is difficult to obtain the characteristics of the aramid fiber as a high strength fiber.

  The aramid polymer and the method for producing an aramid fiber in the present invention are described in, for example, British Patent No. 1501948 and US Pat. No. 3,738,964.

  Specific examples of the aramid fiber thus obtained include an aramid polymer composed of an aromatic dicarboxylic acid component and an aromatic diamine component, or an aromatic aminocarboxylic acid component, or a fiber composed of a copolymer aramid polymer thereof. Examples thereof include polyparaphenylene terephthalamide fiber, copolyparaphenylene 3,4'-oxydiphenylene terephthalamide fiber, and polymetaphenylene terephthalamide fiber. Among them, the copolyparaphenylene • 3,4′-oxydiphenylene terephthalamide fiber is particularly preferable because it has high strength and excellent durability.

  In order to obtain an aramid fiber having a carbon black surface area ratio of 10 to 70%, a method of bleeding out carbon black on the fiber surface by adjusting the spinning conditions of the aramid fiber may be considered. However, as described above, carbon black is included. A method of exposing carbon black on the fiber surface in the above ratio by discharging a spinning solution (dope) from a nozzle, solidifying in a coagulation bath, removing the solvent, applying an abrasive to the dried aramid fiber and performing a rubbing treatment Is desirable. In addition, the rubbing treatment is performed using the stretching step, and the aramid polymer constituting the fibers is highly oriented and the aramid fibers are scraped by performing contact heating and stretching with a metal or ceramic heater. The carbon black is preferably exposed on the fiber surface. In this case, the inorganic fine particle is not particularly limited as long as it is a material that can withstand a temperature of 500 ° C. or higher, but inorganic fine particles, particularly talc and osmos are preferable from the viewpoint of availability. When an abrasive is not used, rubbing is insufficient and the effect of the present invention is not sufficiently obtained.

  As the heater, a hot plate is preferably used, and the material of the hot plate is not particularly limited, but stainless steel, particularly SUS316, is preferable from the viewpoint of heat resistance and wear resistance. The surface roughness of the hot plate is preferably in the range of 1.0 to 5.0 μm. When the surface roughness is lower than 1.0 μm, the friction with the hot plate becomes so large that the yarn breakage frequently occurs during rubbing, and continuous contact heating and drawing are difficult. On the other hand, if the surface roughness is larger than 5.0 μm, the friction with the hot plate is small and the rubbing is insufficient, and the effect of the present invention tends not to be obtained.

  The strength of the aramid fiber is suitably 18 cN / dtex or more, more preferably in the range of 20 to 30 cN / dtex. When the strength is less than 18 cN / dtex, it is difficult to obtain excellent durability because the strength is not sufficient for long-term use. Although it is not necessary to specifically limit the single fiber fineness and the yarn fineness in the case of using the long fiber, suitable single fiber fineness is 0.55 to 5.5 dtex, particularly 1.1 to 3.3 dtex, and the yarn fineness is A range of 110 to 5500 dtex, particularly 330 to 3300 dtex is suitable.

  Since the aramid fiber of the present invention is excellent in rubber adhesiveness, for example, a tire reinforcing material in which the fiber is interdigital, a transmission belt and a rubber hose reinforcing material in a woven shape, and a belt reinforcement kneaded in rubber as a cut fiber Useful as a material.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.

<Measurement and evaluation method>
(1) Fineness Measured according to JIS-L-1015 B method.

(2) Tensile strength, elongation at break, modulus Using tensile tester (manufactured by INSTRON Co., Ltd., trade name: INSTRON, model: 5565 type), based on the procedure of ASTM D885, using the yarn test chuck, the following The tensile test of conditions was performed and the tensile strength was measured.
Temperature: Room temperature Measurement sample length: 250mm
Chuck pulling speed: 100mm / min
Initial load: 0.35 cN / dtex
Distance between chucks: 250 mm
Test start method: Slack start method

(3) Average particle diameter It calculated | required by the particle size distribution calculation based on the laser diffraction / scattering method using the particle size distribution meter (The Shimadzu Corporation make, brand name: SALD-200V ER).

(4) Rubber Adhesion Using a tensile tester (manufactured by INSTRON, trade name: INSTRON, model: 5565 type) and using a yarn test chuck based on the procedure of ASTM D885, a tensile test under the following conditions is performed. The tensile strength was measured.
Temperature: Room temperature Measurement sample length: 100mm
Chuck pulling speed: 20mm / min
Initial load: 0.35 cN / dtex
Distance between chucks: 50 mm
Test start method: Slack start method

(5) Carbon black surface area ratio Irradiated with UV excitation light using an epi-illumination fluorescence microscope (Nikon ECLIPSE E600), capturing 50 digital images at a magnification of 100 times at a length of 20 cm in the fiber axis direction, Image processing was performed, the area of the black part of the fiber was (b), the total surface area of the fiber was (S), and each area was measured, and the carbon black surface area ratio was determined from the formula (1).
Carbon black surface area ratio = (b) / (S) × 100 (%) (1)

(6) Surface roughness of heater (hot plate) The arithmetic average height measured according to JIS B 0601 was defined as the surface roughness.

[Example 1]
Carbon black (MPS-1100 manufactured by Dainichi Seika Co., Ltd.) having an average particle size of 5 μm was used. Here, carbon black was dispersed by using a bead mill (Nano Grain Mill) manufactured by Asada Tekko Co., Ltd. to prepare an N-methyl-2-pyrrolidone (NMP) dispersion. At this time, 0.3 mm zirconia beads were used as media.
This carbon black dispersion and NMP were mixed with NMP solution of copolyparaphenylene 3,4'-oxydiphenylene terephthalamide (aramid polymer having a copolymerization molar ratio of 1: 1, manufactured by Teijin Techno Products) at a concentration of 6% by weight. The carbon black content in the obtained dope was added at a ratio of 15% by weight based on the total weight of the aromatic polyamide, and the mixture was stirred and mixed at a temperature of 80 ° C. for 4 hours. Using the obtained dope, it was discharged from a spinneret with 667 holes, spun into an aqueous solution with an NMP concentration of 30% by weight through an air gap of about 10 mm (semi-dry semi-wet spinning method), washed with water, Then, an abrasive (talc manufactured by Fuji Talc Kogyo Co., Ltd., product name: LMRA200, average particle size: 1.9 μm) was applied, and the temperature was 500 ° C. on a hot plate made of SUS316L having a surface roughness of 3.7 μm. Then, the aramid fiber added in a state in which the carbon black was well dispersed was obtained by winding after contact stretching at 10 times.
As a result, the carbon black surface area ratio of the obtained aramid fiber was 10%, and the peel strength was 8.6N.

[Example 2]
Aramid fibers were obtained in the same manner as in Example 1 except that the amount of carbon black added was 50% by weight. The properties of the obtained aramid fiber are shown in Table 1.

[Example 3]
An aramid fiber was obtained in the same manner as in Example 1 except that the amount of carbon black added was 5% by weight. The properties of the obtained aramid fiber are shown in Table 1.

[Example 4]
Aramid fibers were obtained in the same manner as in Example 1 except that the hot plate surface roughness was 1.1 μm. The properties of the obtained aramid fiber are shown in Table 1.

[Example 5]
Aramid fibers were obtained in the same manner as in Example 1 except that the hot plate surface roughness was 4.8 μm. The properties of the obtained aramid fiber are shown in Table 1.

[Comparative Example 1]
Aramid fibers were obtained in the same manner as in Example 1 except that the amount of carbon black added was 1% by weight. The properties of the obtained aramid fiber are shown in Table 1.

[Comparative Example 2]
An aramid fiber was produced in the same manner as in Example 1 except that the amount of carbon black added was 80% by weight. However, many fibers were broken during spinning, and the fiber could not be obtained.

[Comparative Example 3]
Aramid fibers were obtained in the same manner as in Example 1 except that the hot plate surface roughness was 0.5 μm. The properties of the obtained aramid fiber are shown in Table 1.

[Comparative Example 4]
Aramid fibers were produced in the same manner as in Example 1 except that the surface roughness of the hot plate was 6.5 μm. However, many yarns were spun during spinning, and the fibers could not be obtained.

[Comparative Example 5]
When the aramid fiber was drawn, an aramid fiber was obtained in the same manner as in Example 1 except that no abrasive was used. The properties of the obtained aramid fiber are shown in Table 1.

[Comparative Example 6]
In stretching the aramid fiber, an aramid fiber was obtained in the same manner as in Example 1 except that the abrasive was not used and the thermal stretching was performed without contact with the hot plate. The properties of the obtained aramid fiber are shown in Table 1.

[Comparative Example 7]
Aramid fibers were obtained in the same manner as in Example 2 except that the aramid fibers were stretched without using an abrasive and subjected to thermal stretching in a non-contact manner with respect to the hot plate. The properties of the obtained aramid fiber are shown in Table 1.

  The rubber reinforcing aramid fiber of the present invention has remarkably improved rubber adhesion, and can be suitably used for rubber materials such as tires, belts and hoses.

Claims (6)

  An aramid fiber composed of an aramid polymer, wherein the aramid fiber contains carbon black having an average particle size of 10 μm or less, and a ratio of the area of the carbon black to a total surface area of the aramid fiber is 10 to 70%. Aramid fiber for rubber reinforcement characterized by the above.   The aramid fiber for rubber reinforcement according to claim 1, wherein the content of carbon black is 3 to 50% by weight based on the weight of the aramid fiber.   The aramid fiber for rubber reinforcement according to claim 1, wherein at least a part of the carbon black is exposed on the fiber surface by rubbing the surface of the aramid fiber.   The rubber material using the aramid fiber for rubber reinforcement according to any one of claims 1 to 3.   A spinning solution composed of an aramid polymer, carbon black having an average particle diameter of 10 μm or less of 3 to 50% by weight based on the weight of the aramid polymer, and a solvent is discharged from a nozzle, solidified in a coagulation bath, desolvated, and dried. Aramid fiber is produced by adding an abrasive to the aramid fiber and rubbing the aramid fiber to produce an aramid fiber having a carbon black area ratio of 10 to 70% of the total surface area of the aramid fiber. A method for producing an aramid fiber for rubber reinforcement.   The method for producing an aramid fiber for rubber reinforcement according to claim 5, wherein the rubbing treatment is contact heating drawing with a heater.