KR20130133348A - Dope dyed aramid short fiber and process of manufacturing the same - Google Patents

Abstract

The present invention relates to a dope-dyed aramid short fiber and a manufacturing method thereof wherein the dope-dyed aramid short fiber is composed of a wholly aromatic polyamide including one or more kinds of coloring substances selected from a gray pigment, a black pigment, a gray dye, and a black dye; an L^* value of the aramid short fibers which is brightness index is 20 to 70; a length of the aramid short fibers is 2 mm or less; a drainability of the aramid fibers is below 500 mL; and a specific surface area of the aramid short fiber is 5 to 12 m^2/g. The dope-dyed aramid short fiber according to the present invention has a gray or black color instead of a yellow color specific to an aramid short fiber because the dope-dyed aramid short fiber includes a gray or black coloring substance. Accordingly the dope-dyed aramid short fiber according to the present invention is not discriminated when the dope-dyed aramid short fiber is used as a stiffener for brake pads, clutches, gaskets, etc. because the color of the dope-dyed aramid short fiber is similar to that of other materials such as brake pads, thereby improving the appearance thereof and preventing doubt about performance thereof.

Description

Primary aramid short fibers and a method of manufacturing the same {Dope dyed aramid short fiber and process of manufacturing the same}

The present invention relates to a short primary aramid fibers and a method for producing the same, more specifically, a short primary aramid fibers having a gray or black color instead of the inherent yellow of the aramid short fibers and the same It relates to a manufacturing method.

Fibrous and nonfibrous reinforcements have been used for many years in friction products, seal products and other plastic or rubber products. Such reinforcements typically should exhibit high wear and heat resistance.

Asbestos fibers have been generally used as fibrous reinforcing materials, but have been found to be harmful to humans, and their use is prohibited. Therefore, alternatives to various asbestos fibers have been proposed, and one of the most noticed among them is aramid short fibers produced using aramid fibers. Aramid short fibers are used as a reinforcing material for a variety of articles, for example, widely used as a reinforcing material such as brake pads, clutches, gaskets.

Generally, wholly aromatic polyamide fibers, collectively referred to as aramid fibers, include para-aramid fibers and meta-aramid fibers having a structure in which the benzene rings are connected linearly through an amide group (-CONH). Para-aramid fiber has excellent properties such as high strength, high elasticity and low shrinkage. It has a strong strength enough to lift up 2 tons of automobile with a thin thread of about 5mm thickness, It has been used for various applications in high-tech industries. In addition, aramid fibers are blackened at 500 or more, and thus are attracting attention in fields requiring high heat resistance.

Aramid fiber is a process for producing a wholly aromatic polyamide polymer by polymerizing an aromatic diamine and an aromatic dieside halide in a polymerization solvent containing N-methyl-2-pyrrolidone, dissolving this polymer in a concentrated sulfuric acid solvent to prepare a spinning dope After the step of spinning through the spin dope through the spinneret to pass through the non-coagulant fluid and the coagulation bath sequentially to produce a filament, and the step of washing and drying the filament is produced.

Typically, short aramid fibers are produced by cutting the aramid filament prepared as described above to produce short fibers, and then crushed (milled) the cut short fibers between two disks.

However, conventional aramid short fibers have a yellow color, which is a unique color of aramid polymers, and thus, when used as a reinforcement material such as brake pads, clutches, and gaskets, they are easily colored due to color differences with other materials such as brake pads, which are usually gray or black. There was a problem that was identified and resulted in a lack of aesthetics and doubts about performance.

SUMMARY OF THE INVENTION An object of the present invention is to provide a primary aramid short fiber having a gray or black color and a manufacturing method thereof so that the original aramid color included in the brake pad is not identified when used as a reinforcing material such as a brake pad.

In order to achieve the above object, in the present invention, the spinning dope in which the wholly aromatic polyamide polymer is dissolved in a concentrated sulfuric acid solvent is spun, solidified, washed and dried to obtain a wholly aromatic polyamide filament, and then the wholly aromatic polyamide filament. When the aramid short fibers are prepared by cutting, dissociating and beating the first aramid group having a gray or black color by adding one or more coloring materials selected from gray pigment, black pigment, gray dye and black dye to the spinning dope. Prepare the fibers.

The primary aramid short fibers according to the present invention exhibit a gray or black color instead of yellow, which is the unique color of the aramid short fibers.

As a result, when the original aramid short fibers according to the present invention is used as reinforcement materials such as brake pads, clutches, and gaskets, the original aramid short fibers are not identified due to color differences in the final product, so the aesthetics are excellent, and doubts about performance are also prevented. Can be.

Hereinafter, the present invention will be described in detail.

First, the primary aramid short fibers according to the present invention is composed of a wholly aromatic polyamide polymer containing at least one coloring material selected from gray pigments, black pigments, gray dyes and black dyes, the L * value of the brightness index is It is 20-70, length is 2 mm or less, freeness is 500 mL or less, and the specific suface area is 5-12 m <2> / g, It is characterized by the above-mentioned.

The content of the coloring material is preferably 0.01 to 10 parts by weight based on 100 parts by weight of the wholly aromatic polyamide polymer.

If the content of the coloring matter is less than 0.01 parts by weight, the L * value of the brightness index is greater than 70, which is close to yellow, which is an inherent color of the aramid short fibers. The spinning processability of the aromatic polyamide filament is lowered, which is not preferable.

When the L * value of the brightness index exceeds 70, there is a problem of approaching yellow, which is an intrinsic color of the aramid short fibers, and when the L * value of the brightness index is less than 20, the content of the coloring material becomes too high, so that the polyamide filament The problem that the spinning fairness falls is caused.

The brightness index L * value is measured using a colorimeter (manufacturer: Minolta) having a model name chromater CR-300.

The higher the brightness index L *, the closer it is to white; the lower the brightness, the closer to black.

When the length of the said original aramid short fiber exceeds 2 mm, it distorts in a final product, and dispersibility falls.

The degree of freedom of the native aramid short fibers (Canada Standard Freeness) is determined by the degree of fibrillation of the aramid short fibers in the beating process.

In other words, if the degree of fibrillation is excellent, the degree of freedom of the primary aramid short fibers is lowered, which indicates that the primary aramid short fibers have excellent dispersibility.

Therefore, when the degree of freedom of the original aramid short fibers exceeds 500 mL, the dispersibility of the original aramid short fibers included as a reinforcing material in a final product such as a brake pad is not preferable.

The degree of freedom of the primary aramid short fibers is a value measured by the Canadian standard degree of freedom test method of KS M ISO 5267-2.

When the specific surface area of the primary aramid short fibers is less than 5 m 2 / g, when used as a reinforcing material such as a brake pad, the adhesive strength with the matrix resin component is lowered, which is undesirable.

In the present invention, the specific surface area of the primary aramid short fibers was measured by using micromeritics (Micromeritics: Flowsorb II 2300). This is applied to measure the area of the surface of the material with the nonuniform surface by weight. First, the U-shaped glass tube into which the sample (the original aramid short fiber) is inserted is strongly passed through nitrogen to remove moisture to accurately measure the weight of the glass tube. After filling the sample into the glass tube, the weight is again measured to obtain the sample weight. Nitrogen gas is injected into one inlet of the U-shaped glass tube filled with the sample for a predetermined time and nitrogen gas is discharged to the other inlet to adsorb the nitrogen gas to the sample, and the surface area of the sample is calculated by the amount of nitrogen gas adsorbed to the sample .

Specific surface area (m 2 / g) = surface area (m 2) / sample weight (g)

Next, look at the manufacturing method of the primary aramid short fibers according to the present invention.

The present invention by spinning, coagulation, washing and drying the spinning dope in which the wholly aromatic polyamide polymer dissolved in a concentrated sulfuric acid solvent to prepare a wholly aromatic polyamide filament and then cut, dissociate and betray the wholly aromatic polyamide filament When preparing the aramid short fibers is characterized in that the spinning dope is added with at least one colorant selected from gray pigments, black pigments, gray dyes and black dyes.

In this case, it is preferable that the amount of the coloring material in the spinning dope is 0.01 to 10 parts by weight based on 100 parts by weight of the wholly aromatic polyamide polymer in the spinning dope.

Hereinafter, the Example of the method of manufacturing the primary aramid short fiber of this invention is demonstrated concretely.

The coloring material described above in spinning dope prepared by dissolving an aromatic polyamide polymer having an intrinsic viscosity (IV) of 5.0 to 7.0, for example poly para-phenylene terephthalamide (PPD-T) in concentrated sulfuric acid solvent. After the addition, the spinned dope containing the coloring material was spun by using spinnerets, and then coagulated in a coagulation bath through an air gap to dissolve the primary aramid filament. ).

Next, the sulfuric acid remaining in the obtained original aramid filament is removed. The sulfuric acid remaining in the filament can be removed through a washing process using water or a mixed solution of water and an alkali solution.

Subsequently, a drying process for removing moisture remaining in the original aramid filament is performed in a drying roll, and the dried original aramid filament is wound with a winder.

Next, the wound original aramid filament is cut using a rotary cutter to produce a fixed length of the original aramid short fibers.

Next, water washing is performed to remove foreign matters in the primary aramid short fibers, that is, fine powder, emulsion, etc., but it is preferable to carry out at a temperature higher than room temperature in order to easily remove the foreign matters.

Subsequently, the washed original aramid short fibers are added to the dissociation unit and dispersed together with water to carry out a dissociation process of forming a homogeneous slurry. The dissociation process is preferably performed at a temperature higher than room temperature to further remove the remaining oil and the like and to improve the dispersibility of the short aramid fibers. Through the dissociation process, the primary aramid short fibers are separated into a plurality of monofilaments. As for the density | concentration of the original aramid short fiber of the said slurry, 1.0 to 2.0 weight% is preferable.

Subsequently, a slurry uniformly dispersed in water is introduced into the high resolution portion through the dissociation step to perform a beating process in which the original aramid short fibers are beaten and beaten. A refiner is provided in the high portion to separate and cut the original aramid short fibers as well as to fibrillate to produce fibrillated original aramid short fibers having an average length of the original aramid short fibers of 2 mm or less.

Optionally, if the fibrillation of the short aramid fibers does not proceed smoothly, the dissociation step and the beating step may be repeated.

The slurry containing the fibrillated original aramid short fibers through the beating process is made into a sheet by a paper forming unit, and then a squeezing process for first removing water from the paper is carried out by two rolls. It is carried out in a press section composed of a roll.

The paper first removed from the press unit is dried in the drying unit to remove moisture secondly.

The dried paper is then crushed in a crushing unit to form the final distal aramid short fibers.

The final raw aramid short fibers thus prepared are compressed and packed in a predetermined unit in a wrapping unit and then transported to a destination.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples. However, the protection scope of the present invention is not limited by the embodiments described later.

Example 1

The aromatic polyamide polymer was dissolved in 100% sulfuric acid solvent to prepare a spinning dope having an intrinsic viscosity (IV) of 5.5, and then 0.5 parts by weight of a gray pigment to 100 parts by weight of the polyamide polymer was added to the spinning dope.

Next, the primary aramid filament was prepared by spinning the spinning dope with the gray pigment added through the spinneret, and then solidifying and winding it through the air gap.

Next, the original aramid filament was cut by using a rotary cutter to prepare a basic aramid short fiber (Staple) having a length of 3 cm.

Next, after washing the prepared original aramid short fibers, 100 kg of the original aramid short fibers were dispersed in 10,000 L of pure water to prepare a homogeneous slurry.

Next, after the prepared slurry was put into a beating device equipped with a refiner, and then beating for 60 minutes, the slurry after the beating process was dried in a paper form to remove water from the squeegee roll, dried, and then crushed by a grinder. Aramid short fibers were prepared.

The results of measuring various physical properties of the prepared primary aramid short fibers were as shown in Table 2.

Example 2-Example 4

Except that the kind and amount of the coloring material were changed as shown in Table 1, the primary aramid short fibers were prepared in the same manner as in Example 1.

The results of measuring various physical properties of the prepared primary aramid short fibers are shown in Table 1.

Comparative Example 1

Aramid short fibers were prepared in the same manner as in Example 1 except that the coloring material was not added to the spinning dope.

The results of measuring various physical properties of the prepared aramid short fibers were as shown in Table 1.

Manufacturing conditions division Type of coloring matter Addition amount (part by weight) Example 1 Gray pigment 0.5 Example 2 Black pigment 1.5 Example 3 Gray dye 3.5 Salsaye 4 Black dye 5.5 Comparative Example 1 - 0

Physical Properties of Primary Aramid Short Fibers division Example 1 Example 2 Example 3 Example 4 Comparative Example 1 Brightness index
(L * value) 45 30 40 25 87 Length 2 mm 2 mm 2 mm 2 mm 2 mm Yeosu (mL) 420 410 400 420 415 Specific surface area (m &lt; 2 &gt; / g) 8.8 8.9 8.7 8.8 8.9 Coloring matter content
(Parts by weight) 0.5 1.5 3.5 5.5 0

Claims (4)

It is composed of a wholly aromatic polyamide polymer containing at least one colorant selected from gray pigments, black pigments, gray dyes and black dyes, and has a brightness index L * of 20 to 70 and a length of 2 mm or less. The primary aramid short fibers, characterized in that the degree of freedom is 500mL or less, and the specific suface area is 5-12 m 2 / g. The primary aramid short fibers according to claim 1, wherein the coloring material content is 0.01 to 10 parts by weight based on 100 parts by weight of the wholly aromatic polyamide polymer. Spinning dope in which the wholly aromatic polyamide polymer was dissolved in concentrated sulfuric acid solvent was spun, coagulated, washed and dried to prepare an wholly aromatic polyamide filament. In preparing the method, the method for producing the primary aramid short fibers, characterized in that for adding the at least one coloring material selected from the gray pigment, black pigment, gray dye and black dye to the spinning dope. 4. The method for producing primary aramid short fibers according to claim 3, wherein the amount of the coloring material in the spinning dope is 0.01 to 10 parts by weight based on 100 parts by weight of the wholly aromatic polyamide polymer in the spinning dope.