KR20100111866A - Method for manufacturing aramid pulp - Google Patents

Abstract

PURPOSE: A method for manufacturing the same of aramid pulp is provided to manufacture the aramid pulp of the matter desired by using the HM aramid fiber, thereby recycling the wasted HM aramid fiber. CONSTITUTION: An aramid monofilament(1a) is produced by cutting the HM(High Modulus) aramid fiber. The HM aramid fiber has a modulus of 780 to 1100g/d. The HM aramid monofilament is washed. The washing processing is performed in 40 to 70 degree of temperature. The washed HM aramid monofilament is dispersed in the water. Therefore, slurry is manufactured. To generate the fibrillated monofilament, the refining of the slurry is performed.

Description

Method for Manufacturing Aramid Pulp {Method for Manufacturing Aramid Pulp}

The present invention relates to a method for producing aramid pulp, more specifically, by using a high modulus (HM, paramodal aramid fibers) to prepare aramid pulp that satisfies the desired physical properties, the process remaining or manufactured The present invention relates to a method for producing aramid pulp that enables the recycling of abandoned HM aramid fibers.

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 pulp produced using aramid fibers. Aramid pulp is used as a reinforcement for various articles, for example, widely used as a reinforcement for brake pads, clutches, gaskets and the like.

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 is a thin thread of about 5mm thick and has a strong strength enough to lift 2 tons of cars. It is used in various industries in the high-tech industry. In addition, aramid fibers are carbonized at 500 ° C or higher, 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.

Standard para-aramid fibers commonly used in the industry have a modulus of about 650-750 g / d. Recently, HM aramid fibers having a high modulus of 780 to 1100 g / d have attracted attention in terms of dimensional stability. HM aramid fibers can be prepared by heat treatment of aramid filaments dried after washing under constant tension.

In general, aramid pulp has been prepared using ST aramid fibers, more specifically, ST aramid short fibers (chopped fibers) in water between two rotating disks to form fibrillated fibers and then dewatered By a wet fibrillation method for producing pulp or a dry fibrillation method for producing pulp by dry milling aramid fibers between a rotary cutter and a screen.

However, when the pulp is prepared according to the conventional method for producing aramid pulp using HM aramid fibers, the final aramid pulp did not exhibit the physical properties required by the industry. Accordingly, the remaining HM aramid fibers or the HM aramid fibers discarded in the process of being manufactured do not have a recycling method, that is, they cannot be applied to the pulp manufacturing process and are discarded as they are.

Accordingly, the present invention relates to a method for producing aramid pulp that can avoid the problems caused by the above limitations and disadvantages of the related art.

An advantage of the present invention is the use of high modulus (HM) para-aramid fibers to produce aramid pulp that satisfies the desired physical properties, thereby enabling the recycling of ammonia fibers that are left in use or discarded in the process of being produced. It is to provide a method for producing pulp.

Further features and advantages of the invention will be described below, and in part will be apparent from such techniques. Alternatively, other features and advantages of the present invention may be learned from the practice of the present invention. Objects and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

In order to achieve the above advantages, and in accordance with the object of the present invention, cutting the HM aramid fibers having a modulus of 780 to 1100 g / d to make HM aramid short fibers; Washing the HM aramid short fibers; Dispersing the washed HM aramid short fibers in water to prepare a slurry; And refining the slurry to produce a fibrillated monofilament.

It is to be understood that both the foregoing general description and the following detailed description are intended to illustrate or explain the invention, and to provide a more detailed description of the invention in the claims.

According to the method for producing aramid pulp of the present invention, using the high elastic modulus HM aramid fibers to break the existing preconception that the high elastic modulus HM aramid fibers can not produce a pulp having the desired physical properties of the aramid pulp It can manufacture.

Therefore, unlike the conventional method in which only ST aramid fibers are used to prepare aramid pulp, the present invention uses a high modulus HM aramid fiber to make aramid pulp that satisfies desired physical properties. It has the advantage of enabling the recycling of HM aramid fibers left over or discarded in the process of manufacture.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit and scope of the invention. Accordingly, the invention includes all modifications and variations that fall within the scope of the invention as set forth in the claims and their equivalents.

As used herein, the term 'multifilament' refers to a bundle of monofilaments formed by the solidification of the spinning dope spun through the spinneret.

As used herein, the terms 'aramid fiber' and 'aramid filament' refer to aramid multifilament.

'ST aramid fiber' as used herein refers to aramid fiber having a modulus of 650 to 750 g / d.

"HM aramid fiber" as used herein refers to a high modulus aramid fiber having a modulus of 780 to 1100 g / d.

The modulus of aramid fibers used herein is a value obtained by the tensile strength and elongation test method of the fibers of KS K 0323, ISO5079.

Hereinafter, with reference to the accompanying drawings an embodiment of a method for producing aramid pulp of the present invention will be described in detail.

First, ST aramid fibers are produced by the following method using the production system shown in FIG.

Spinning dope prepared by dissolving an aromatic polyamide polymer having an inherent viscosity (IV) of 5.0 to 7.0, for example, poly (paraphenylene terephthalamide: PPD-T) in a concentrated sulfuric acid solvent. After spinning using a spinneret 10, a multifilament is formed by solidifying in a coagulation bath 20 through an air gap.

The multifilament formed as the sulfuric acid escapes from the spinning dope is composed of the same number of monofilaments as the number of holes formed in the spinneret 10. Each of the monofilaments consists of a core layer located at the center of the cross section with respect to its longitudinal direction and a skin layer located at the outer side.

Next, sulfuric acid remaining in the obtained multifilament is removed. Sulfuric acid used in the manufacture of the spinning dope may remain but is not removed completely, although most of the emissions are removed as it passes through the coagulation bath 20. Moreover, when sulfuric acid is added to the coagulating liquid of the coagulation tank 20 in order to make sulfuric acid escape uniformly from a effluent, it is highly likely that sulfuric acid will remain in the multifilament obtained. Since the amount of sulfuric acid remaining in the multifilament may adversely affect the aramid fiber properties no matter how small the amount, it is very important to completely remove the sulfuric acid remaining in the multifilament. Sulfuric acid remaining in the multifilament may be removed through a washing process using water or a mixed solution of water and an alkaline solution.

The washing process may be carried out in a multi-step process, for example, first washing with multi-filament containing sulfuric acid in a first washing tank 30 containing 0.3 to 1.3% of an aqueous caustic solution, and then Second washing with water is carried out in the second washing tank 40 containing 0.01 to 0.1% of a thinner caustic aqueous solution. The first and second flushing rolls 31 and 41 are provided in the first and second flushing tanks 30 and 40, respectively, to move the multifilament.

Subsequently, a drying process for removing moisture remaining in the multifilament is performed in the drying unit 50. In the drying process, the filament may reach the drying roll 51 in the drying unit 50, or the moisture content of the filament may be adjusted by adjusting the temperature of the drying roll 51. ST aramid fiber is obtained by winding up the dried multifilament with the paper tube 60.

On the other hand, HM aramid fibers can be prepared in the same manner as ST aramid fibers, except that the aramid filaments dried after washing with heat under a certain tension.

ST aramid fiber prepared as above is composed of monofilaments having a linear density of 0.7 to 3.0 denier (denier), has a total linear density of 200 to 3,000 denier, strength of 19 to 28 g / d, elongation at break of 3 to 3.5% and Has a modulus of 650-750 g / d. In contrast, HM aramid fibers consist of monofilaments with a fineness of 0.7 to 3.0 denier and have a total fineness of 150 to 3,000 denier, strength of 19 to 28 g / d, elongation at break of 2.5 to 3.5% and 780 To modulus from 1100 g / d.

2 schematically shows a system for producing aramid pulp of the present invention.

First, HM aramid short fibers 1a having a length of about 3 to 10 mm are manufactured by cutting the HM aramid fibers wound around the branch pipe 60 using a rotary cutter (not shown). The length of the HM aramid short fibers 1a can be adjusted by adjusting the blade spacing of the rotary cutter.

Alternatively, the HM aramid short fibers 1a may be prepared by pulverizing the loose filament, that is, the HM aramid fibers not wound around the branch pipe 60, during the spinning process.

According to the present invention, the HM aramid short fibers 1a prepared as above are washed with pure water under a temperature of 40 to 70 ° C. This is to remove the oil contained in the HM aramid short fibers (1a). The reason for removing the emulsion is as follows.

Unlike ST aramid fibers, HM aramid fibers are subjected to a heat treatment process, in which heat-resistant emulsions are used. Eventually, the final HM aramid fiber will contain a heat resistant emulsion. The present inventors have found that the presence of such heat resistant emulsions tends to agglomerate monofilaments with each other, which in turn is an important cause of increasing the freeness of the pulp. Therefore, according to the present invention, the HM aramid short fibers 1a are washed with pure water at a temperature of 40 to 70 ° C for removing such an oil agent. This washing process is preferably repeated until the emulsion content of the HM aramid short fibers 1a is 0.1% by weight or less.

Method for measuring the emulsion content of the HM aramid short fibers (1a) is as follows.

(1) Measuring the weight of the specimen (W ₁ )

(2) drying at 105 ° C. for 2 hours

(3) After leaving for 30 minutes in the desiccator, measure the weight (W ₂ )

(4) 10 minutes treatment with refiner

(5) 2 hours drying at 105 ℃

(6) Measure the weight (W ₃ ) after leaving it for 30 minutes in desiccator

As a refining agent, CCl ₄ , methanol, a methanol mixed solution, and the like are used, and an oil content (OPU) is calculated by Equation 1 below.

Equation 1: emulsion content (OPU) (% by weight) = (W ₂ -W ₃ ) / W ₁ × 100

On the other hand, ST aramid short fibers 1b are produced in the same manner as the method for producing HM aramid short fibers 1a.

Subsequently, the washed HM aramid short fibers 1a and the ST aramid short fibers 1b are dispersed together in water in the first tank 110 to perform a dissociation process of forming a homogeneous slurry. At this time, it is preferable that the weight ratio of HM aramid short fiber 1a with respect to ST aramid short fiber 1b is 1 or less. Thus, by using the ST aramid short fibers 1b together with the HM aramid short fibers 1a, the adverse effects due to the trace amount of the emulsion that may remain in the HM aramid short fibers 1a can be offset.

The dissociation process is performed for about 1 hour at a temperature of 30 to 40 ℃. Through the dissociation process, each of the HM aramid short fibers 1a and the ST aramid short fibers 1b are separated into a plurality of monofilaments. The concentration of monofilaments in the slurry is 1.0 to 1.5% by weight.

The pH of the slurry is managed between 6.5 and 8.5. If the pH of the slurry is less than 6.5, the monofilaments tend to aggregate among themselves, thereby decreasing the dispersibility of the monofilaments. In contrast, when the pH of the slurry exceeds 8.5, the monofilaments are well separated from each other, but the final product pulp breaks down well.

When the HM aramid short fibers 1a and the ST aramid short fibers 1b are dispersed together in water to form a slurry in the first tank 110, the slurry is sent to the second tank 120 to include the mono in the slurry. The filaments are beaten and subjected to refining. A refiner is installed in the second tank 120 to separate the HM aramid short fibers 1a and ST aramid short fibers 1b, which may still be contained in the slurry, into monofilaments, as well as the slurry. The monofilaments included in the cut and fibrillate.

The refiner that can be used in the present invention is, for example, a Double Disk Refiner, but if the monofilaments can be cut and fibrillated, there is no limitation in its kind. The dual disk refiner includes a fixed disk and a rotating disk, which cuts and fibrillates the monofilaments contained in the slurry as the rotating disk rotates and approaches the fixed disk.

According to the present invention, the monofilaments are converted into fibrillated monofilaments 2 having an average length of about 1 to 1.5 mm via a beating process performed in the second tank 120.

The beating process is one of the important processes for determining the freeness (Canada Standard Freeness) of aramid pulp. This is because the degree of fibrillation of monofilament through the beating process and the degree of freedom of aramid pulp are closely related. That is, if the degree of fibrillation of the monofilament is excellent, the freeness of the pulp is lowered, which means that the aramid pulp has excellent dispersibility. On the other hand, when the degree of fibrillation of the monofilament is poor, the degree of freeness of the pulp is high, which means that the aramid pulp has poor dispersibility.

Optionally, a third tank may be further installed for repeating the beating process. In addition, the dissociation and beating process may be repeated by returning the slurry containing the fibrillated fibers 2 discharged from the second tank or the third tank back to the first tank.

The slurry which contains the fibrillated filament 2 through the beating process is made into a sheet 3 by a sheet forming unit 130, and then the moisture is removed from the sheet 3. A squeegeeing process for first removal is performed in a pressing unit 140 composed of two rolls.

The papermaking 4 in which moisture is first removed from the press unit 140 is dried in the drying unit 150 to thereby remove moisture secondly. According to one embodiment of the invention, the drying process is controlled so that the moisture content of the dried papermaking 5 is 15 to 40% by weight.

The dried papermaking 5 is then crushed in a crushing unit 160 to become the final aramid pulp 7.

The final aramid pulp 7 thus prepared is compressed in a wrapping unit 180 in units of about 5.0 to 5.5 kg and then transported to a destination.

Hereinafter, the present invention will be described in detail through examples and comparative examples. However, the following examples are only intended to help the understanding of the present invention, and the scope of the present invention should not be limited thereto.

Example 1

A length of HM aramid short fibers was made by cutting with a rotary cutter an HM aramid fiber having a strength of 20 g / d, an elongation at break of 3.5% and a modulus of 900 g / d. The HM aramid short fibers were washed with pure water at a temperature of 50 ° C. until the emulsion content of HM aramid short fibers became 0.1% by weight.

ST aramid short fibers of a length were made by cutting a ST aramid fiber having a strength of 21 g / d, an elongation of 3.5% and a modulus of 700 g / d using a rotary cutter.

A homogeneous slurry was prepared by dispersing 50 kg of the washed HM aramid fibers and 50 kg of ST aramid short fibers together in 10,000 L of pure water. The slurry thus prepared was put into a refining tank equipped with a double disk refiner having a 20 inch diameter disk, and then bent for 60 minutes to produce fibrillated monofilaments having an average length of 1 mm.

Through the beating process, the slurry containing fibrillated filaments was made into a sheet and then squeezed out moisture contained in the paper by passing between two rolls. Subsequently, the paper was first removed from the press by drying the paper from which the water was first removed at a temperature of 100 ° C. for 2 minutes. The moisture content of the dried paper was 20% by weight.

The dried papermaking was crushed into small pieces 6 using a grinder to produce the final aramid pulp. The water content of the final aramid pulp was 5% by weight.

Examples 2-5 and Comparative Examples 1-2

Aramid pulp was prepared in the same manner as in Example 1 except that the emulsion content of the HM aramid short fibers washed with water was as shown in Table 1 below.

TABLE 1

Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Emulsion content (% by weight) 0.08 0.06 0.03 0.01 0.12 0.15

Comparative Example 3

Aramid pulp was prepared in the same manner as in Example 1 except that the washing process for HM aramid short fibers was omitted. The emulsion content of unwashed HM aramid short fibers was 1% by weight.

Comparative Example 4

Aramid pulp was prepared in the same manner as in Example 1 except that only 100 kg of washed HT aramid short fibers without ST aramid short fibers were dispersed in 10,000 liters of pure water.

The freeness of each of the aramid pulp prepared by Examples 1 to 5 and Comparative Examples 1 to 4 was measured by the following method to obtain the results as shown in Table 2 below.

Freedom Measurement of Aramid Pulp

The freeness (ml) of aramid pulp was measured by the Canadian Standard Freeness (CSF) test method of KS M ISO 5267-2.

TABLE 2

Example
One Example
2 Example
3 Example
4 Example
5 Comparative example
One Comparative example
2 Comparative example
3 Comparative example
4 Yeosu
(ml) 350 380 380 360 350 390 410 460 400

From Examples 1 to 5 and Comparative Example 3 of Table 2 above, when the washing process for the HM aramid short fibers is not performed, the freeness of the aramid pulp is required in the industry under the influence of the emulsion contained in the HM aramid short fibers. It is much higher than 400 ml.

In addition, from Examples 1 to 5 and Comparative Examples 1 and 2 of Table 2 above, even if the water washing process for the HM aramid short fibers when the emulsion content of the HM aramid short fibers washed with water exceeds 0.1% by weight Edo also shows that the freeness of aramid pulp still exceeds the industry's required 400 ml.

On the other hand, from Examples 1 to 5 and Comparative Example 4 of the above Table 2, aramid pulp prepared only with HM aramid short fibers, although the freeness is 400 ml or less, satisfies the physical properties required by the industry, ST aramid short fibers It can be seen that the degree of freedom is somewhat higher when compared to aramid pulp prepared using HM aramid short fibers.

The accompanying drawings are included to assist in understanding the present invention and to form a part of the specification, to illustrate embodiments of the present invention, and to explain the principles of the present invention together with the detailed description of the invention.

1 is a view schematically showing a system for producing ST aramid fibers,

2 is a view schematically showing a system for producing aramid pulp of the present invention.

<Explanation of Signs of Major Parts of Drawings>

1a: HM Aramid Short Fiber 1b: ST Aramid Short Fiber

2: fibrillated monofilament 3: papermaking

4: Primary moisture-free paper 5: Dried paper

6: aramid pulp

10: spinneret 20: coagulation tank

30: first water washing tank 31: first water washing roll

40: 2nd water washing tank 41: 2nd water washing roll

50: drying unit 51: drying roll

60: winder 110: first tank

120: second tank 130: grass paper forming portion

140: press part 150: drying part

160: shredding unit 170: packing unit

Claims (11)

Cutting HM aramid fibers having a modulus of 780 to 1100 g / d to make HM aramid short fibers; Washing the HM aramid short fibers; Dispersing the washed HM aramid short fibers in water to prepare a slurry; And Refining the slurry to produce a fibrillated monofilament. The method of claim 1, The washing step is a method for producing aramid pulp, characterized in that it is carried out repeatedly until the oil content of the HM aramid short fibers is 0.1% by weight or less. The method of claim 1, The washing step is a method for producing aramid pulp, characterized in that carried out at a temperature of 40 to 70 ℃. The method of claim 1, The HM aramid short fibers are washed with pure water, the method for producing aramid pulp. The method of claim 1, Cutting ST aramid fibers having a modulus of 650 to 750 g / d to make ST aramid short fibers, The ST aramid short fibers are dispersed in the water together with the washed HM aramid short fibers to make a slurry. The method of claim 5, When the ST aramid short fibers are dispersed in the water together with the washed HM aramid short fibers, the weight ratio of the washed HM aramid short fibers to the ST aramid short fibers is 1 or less. . The method of claim 1, The method of producing aramid pulp, characterized in that further comprising the step of making paper from the slurry containing the fibrillated monofilament through the beating process. The method of claim 7, wherein A method of producing aramid pulp further comprising the step of squeezing (squeezing) moisture from the paper. The method of claim 8, Method of producing aramid pulp, characterized in that it further comprises the step of drying the papermaking (moisture) is removed through the squeegee. The method of claim 9, The moisture content of the dried papermaking is a method for producing aramid pulp, characterized in that 15 to 40% by weight. The method of claim 9, And crushing the dried paper into a plurality of pieces.

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