KR101144567B1 - Aramid pulp and method for manufacturing the same - Google Patents

Abstract

Aramid pulp, characterized in that the present invention has a frictional electrification voltage of 1,000 V or less, a half life of 1.0 to 2.5 seconds, and a surface resistance of 10 ¹⁰ kPa or less.

Making aramid short fibers, dispersing the short aramid fibers in water to prepare a slurry, beating the slurry to make fibrillated aramid short fibers, and preparing paper from the fibrillated aramid short fibers. It relates to a method for producing aramid pulp, including the step of making, characterized in that the treatment of the antistatic agent before each selected step by selecting one or more of the above steps.

According to the present invention, the aramid fiber treated with the antistatic agent is smoothly dissociated and fibrillated, and the aramid pulp produced has excellent freeness, and has excellent surface resistance and frictional electrification voltage, and then the aramid pulp is applied to the product. When applied, the process proceeds smoothly, and due to the excellent dispersibility, a product having a uniform quality can be manufactured.

Aramid pulp, antistatic, frictional high voltage, surface resistance

Description

Aramid pulp and method for manufacturing the same

The present invention relates to aramid pulp and a method for manufacturing the same, and specifically, by treating the aramid fibers with an antistatic agent, dissociation and beating can proceed smoothly to produce aramid pulp having excellent freeness, and when applied to a product The present invention relates to an aramid pulp capable of expressing excellent fairness and quality and a method of manufacturing the same.

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 made 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 fibers have excellent properties such as high strength, high elasticity, and low shrinkage.The thin aramid fibers are 5mm thick and have a strong strength enough to lift 2 tons of cars. It is used for various purposes 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.

In general, aramid pulp is obtained by cutting aramid filaments to produce aramid short fibers, fibrillated using a beating machine, then made into a papermaking form, then dehydrated and dried.

However, aramid fibers have a large amount of static electricity generated by friction during the chemical structure process, and due to these characteristics, the aramid fibers tend to aggregate among the aramid fibers, so that the dissociation and beating process does not proceed smoothly, resulting in a decrease in fibrillation of short aramid fibers. It was difficult to meet the demand of Yeosu in the industry.

In addition, the produced aramid pulp has a strong property to agglomerate, so that the dispersibility in the manufacture of products such as brakes and gaskets are inferior, so that the aramid pulp is not good bondability with other materials such as minerals, it was not possible to obtain a good quality product.

In addition, since the use of aramid pulp, the use of a variety of products in the development of the frequent use of static electricity, which can threaten the risk of fire and workers' health, the situation was limited to use.

The present invention was derived to solve the above problems, an object of the present invention by treating the aramid fibers with an antistatic agent to smoothly proceed dissociation and beating, aramid pulp having excellent freeness and antistatic properties and its preparation It is about a method.

In order to achieve the above object, the present invention provides an aramid pulp, characterized in that the frictional electrification voltage is 1,000V or less, the half-life is 1.0 ~ 2.5 seconds and the surface resistance is 10 ¹⁰ kPa or less.

On the other hand, the aramid pulp may be treated with an antistatic agent containing one or more selected from phosphate-based, carboxylate-based, sulfate-based and sulfonate-based.

At this time, the antistatic agent is preferably contained in 0.1 to 5% by weight relative to the aramid pulp.

In addition, it is preferable that the aramid pulp has a degree of freedom of 300 to 500 ml.

Another aspect of the present invention to achieve the above object, the step of making aramid short fibers and dispersing the aramid short fibers in water to prepare a slurry and beating the slurry to make the fibrillated aramid short fibers and It provides a method of producing aramid pulp, comprising the step of making a sheet of paper from the fibrillated aramid short fibers, by selecting one or more of the steps to treat the antistatic agent prior to each selected process.

On the other hand, the antistatic agent includes one or more selected from phosphate, carboxylate, sulfate and sulfonate, and 0.1 to 5 for aramid pulp It is preferably contained in weight percent.

According to the present invention, the aramid fiber treated with the antistatic agent is smoothly dissociated and fibrillated, and the aramid pulp produced has excellent freeness, and has excellent surface resistance and frictional electrification voltage, and then the aramid pulp is applied to the product. When applied, the process proceeds smoothly, and due to the excellent dispersibility, a product having a uniform quality can be manufactured.

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

First, the present invention can use a variety of antistatic agents. In particular, in the present invention, it is preferable to use one or more compounds selected from phosphate, carboxylate, sulfate and sulfonate compounds, wherein the antistatic agents are aramid. And good adhesiveness can be expressed and excellent antistatic property can be exhibited.

On the other hand, it is preferable that the antistatic agent contains 0.1 to 5.0 weight% in solid content ratio with respect to the manufactured aramid pulp 6. If the content of the antistatic agent is too small, the antistatic performance is insufficient. If the content is too high, the aramid physical properties are degraded.

The antistatic agent of the present invention can be imparted to aramid fibers by various methods. For example, there is a spray method for simply treating the antistatic agent to the aramid fiber by using the injection nozzle 180, another method is to immerse the aramid fiber in a container in which the antistatic agent is stored, and then control the pickup rate There is an immersion method that can adjust the content of the inhibitor.

Meanwhile, the antistatic agent may be strongly adhered to the aramid fiber through heat treatment after the antistatic agent is applied to the aramid fiber.

Imparting such an antistatic agent to the aramid fibers can be performed during various processes. The present invention may treat the antistatic agent in one or more of several manufacturing steps for producing the aramid pulp 6.

First, the method of providing an antistatic agent in the process of manufacturing an aramid filament is demonstrated. Aramid filament can be produced by the following method.

Spinning dope prepared by dissolving an aromatic polyamide polymer prepared by a conventional method, for example, poly (paraphenylene terephthalamide: PPD-T) in a concentrated sulfuric acid solvent, After spinning by using a coagulation unit (coagulation unit) (coagulation unit) through the air gap (air gap) to form a filament (filament).

Subsequently, after the sulfuric acid remaining in the obtained filament is removed in the water washing part 30, the water remaining in the filament is removed in the heat treatment part 50 and wound up in the winder 60 to obtain aramid filament.

At this time, the present invention can treat the antistatic agent during the process for producing the aramid filament described above. Figure 1 shows an embodiment of the present invention, the aramid filaments washed in the water washing unit 30 can be applied to the antistatic agent at a constant pickup rate in the antistatic treatment unit 40. The antistatic treatment unit (40) is provided with a container in which an antistatic agent is stored and a driving roll partially immersed in the storage container, such that the rotational speed of the driving roll, the concentration of the solution, the upper surface of the washed aramid filament and the driving roll and The pickup rate is adjusted by the pressure, etc. The filament picked up with the antistatic agent may be dried and solidified in the heat treatment unit 50 using a drying roll to improve adhesion strength between the aramid fibers and the antistatic agent.

In another embodiment, the antistatic treatment unit 40 may be provided between the heat treatment unit 50 and the winder 60, and may be immediately wound up after applying the antistatic agent to the heat treated aramid filament. On the other hand, it is preferable to perform the said method, when adhesiveness between antistatic agent and aramid filament is favorable.

Although it is preferable to use aramid filament as a material of the aramid pulp 6 of the present invention, the aramid pulp 6 may be produced by selectively using waste dope generated during the spinning process. The waste dope is preferably crushed, cut and oriented using a grinder because the orientation crystallinity is inferior to that of the aramid filament. Subsequently, a spray method or a method of appropriately adjusting the pick-up rate using a squeezing roll after dipping may be used for the aramid fibers produced in the form of short fibers by a mill. Then, heat treatment may be optionally performed.

Next, the antistatic agent can be treated during the process of producing the aramid pulp. Figure 2 schematically illustrates one embodiment of making aramid pulp of the present invention.

The aramid filament 1 having a length of about 3 to 10 mm is prepared by cutting the prepared aramid filament using a rotary cutter (not shown). The length of the aramid short fibers 1 can be adjusted by setting the blade spacing of the rotary cutter.

On the other hand, in the present invention, the aramid short fibers (1) obtained after cutting the aramid filament can be subjected to an optional heat treatment after applying the antistatic agent using the conventional method described above.

In some cases, before the antistatic agent is treated on the short aramid fibers 1, the short aramid fibers 1 may be washed at a temperature of 40 to 70 ° C. to remove foreign substances.

Subsequently, the prepared aramid short fibers 1 are dissociated together in water in the dissociation unit 110 to perform a dissociation process of making a homogeneous slurry. When the slurry is formed, it is sent to the high anatomical 120 to beat the aramid short fibers (1) contained in the slurry to perform a beating process.

The short aramid fibers (1) have a strong tendency to aggregate with each other in the molecular structure. Therefore, it is not easy to uniformly disperse the aramid short fibers 1 in the aqueous solution in the dissociation step. If the aramid short fibers (1) are not well dispersed, the aramid short fibers (1) aggregated during the beating process does not form fibrils smoothly.

Therefore, in the present invention, by treating the aramid short fibers 1 with the antistatic agent before the dissociation or beating process, the aramid short fibers 1 may be removed to agglomerate to effectively perform the dissociation and beating process.

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, if the degree of fibrillation of the monofilament is poor, the degree of freeness of the pulp is high, which means that the aramid pulp dispersibility is poor. Therefore, if the fibrillation is bad, as the dissociation and beating process must be repeated, the production cost increases.

However, if the degree of freeness is too low, that is, if the monofilament is excessively fibrillated, the physical properties of the aramid pulp are poor, and thus the quality required by the company in the application of the product cannot be obtained. Therefore, the produced aramid pulp needs to have an appropriate freeness, and the aramid pulp of the present invention preferably has a freeness of 300 to 500 ml.

Next, the slurry containing the fibrillated filament through the beating process is made of paper by the paper forming unit 130. Subsequently, a squeegeeing process for first removing moisture from the paper is performed in the press unit 140. The paper first removed moisture from the press unit 140 is dried in the drying unit 150 to remove the secondary water.

On the other hand, optionally, the prepared papermaking agent can be treated with an antistatic agent, and after the antistatic agent is applied to the papermaking paper from which moisture is removed by the squeegee roll, it can be dried in the drying unit 150.

Subsequently, the dried papermaking is crushed in the crushing unit 160 to become the final aramid pulp 6. The final aramid pulp 6 thus prepared is compressed and packed in a predetermined unit in the packaging unit 170 and then transported to the destination.

Alternatively, the crushed aramid pulp 6 may be treated with an antistatic agent by the above-described method.

The aramid pulp 6 according to the present invention preferably has a frictional electrification voltage of 1,000 V or less, a half life of 1.0 to 2.5 g seconds, and a surface resistance of 10 ¹⁰ kPa or less. If the aramid pulp 6 does not satisfy the above electrical properties, the subsequent process may not proceed smoothly, and the dispersibility may be poor, and thus an excellent product may not be manufactured.

Hereinafter, the present invention will be described in detail through examples and comparative examples. However, the following examples are not intended to limit the scope of the present invention by way of helping the understanding of the present invention.

Example  One

Spinning dope was prepared by dissolving the aromatic polyamide polymer in 100% sulfuric acid solvent. The filament was manufactured by spinning the spin dope using the spinneret 10 and then solidifying the solidified part 20 through the air gap. The filament is washed in the water washing unit 30, and then removes water using a water removal device (not shown), and the antistatic composition containing a carboxylate-based 2,2-thiobisacetic acid bis (2-ethylhexyl) ester The pick-up ratio was appropriately controlled by adjusting the rotational speed and the concentration of the roll in contact with the roll installed in the antistatic treatment unit 40, and then heat-treated in the heat treatment unit 50 set at 120 ° C. After that, the aramid filament treated with the antistatic agent was obtained by winding the winder 60.

The aramid filament was cut using a rotary cutter to make aramid short fibers 1 of a predetermined length, and then the short aramid fibers 1 were washed in a washing unit 100 at 50 ° C. After dispersing the washed aramid short fibers (1) in water to prepare a homogeneous slurry, the prepared slurry was added to the beating portion 120 equipped with a double disk refiner, and then begged for 1 hour to form a fibrillated aramid. Short fibers 2 were prepared.

The paper 3 was made from the slurry including the fibrillated short fibers, and then passed through a squeegee roll to remove moisture and dried in the drying unit 150. The dried papermaking paper 5 was crushed using a grinder to prepare a final aramid pulp 6 containing 1% by weight of an antistatic agent in a solid content ratio.

Example  2

In the process for producing the aramid pulp 6, the antistatic agent is a solid component by the same method as in Example 1, except that the antistatic agent is further treated by spraying on the paper 4 from which moisture has been removed. Aramid pulp (6) containing 1.5% by weight in proportion was prepared.

Example  3

In the process of manufacturing the aramid filament, after washing the coagulated aramid filament in the water washing unit 30, the antistatic agent is not treated, except that the antistatic agent is treated only immediately before winding and not dried. By the same method as 1, an aramid pulp 6 containing 0.8 wt% of an antistatic agent in a solid content ratio was prepared.

Example  4

Spinning dope was prepared by dissolving the aromatic polyamide polymer in 100% sulfuric acid solvent. The filament was manufactured by spinning the spin dope using the spinneret 10 and then solidifying the solidified part 20 through the air gap. The filament was washed in the water washing part 30 and then heat treated at 120 ° C., and then wound up with a winder 60 to obtain an aramid filament.

The aramid filaments were cut using a rotary cutter to make aramid short fibers 1 of a predetermined length, and the aramid short fibers 1 were washed in a washing unit 100 at 50 ° C. After removing water (not shown) from the washed aramid short fibers (1), an antistatic composition containing a carboxylate-based 2,2-thiobisacetic acid bis (2-ethylhexyl) ester is appropriately sprayed. After giving, it dried. The washed aramid short fibers (1) was dispersed in water to prepare a homogeneous slurry. The fibrillated aramid short fibers 1 were prepared by injecting the slurry thus prepared into the bent portion 120 equipped with the double disk refiner for 1 hour.

The paper was made from the slurry containing the fibrillated short fibers, and then passed through the squeegee roll to remove moisture and dried in the drying unit 150. The dried papermaking was crushed using a grinder to prepare a final aramid pulp (6) containing 1.0% by weight of an antistatic agent in a solid content ratio.

Conventional example

Aramid pulp 6 was prepared in the same manner as in Example 1 except that the antistatic agent was not treated.

Comparative example  One

Aramid pulp 6 was prepared in the same manner as in Example 1 except that the pick-up rate was adjusted in the antistatic agent treatment step so that the antistatic agent was contained 0.05% by weight in solid content.

Comparative example  2

In the process of manufacturing the aramid filament, without treating the antistatic agent, and making a paper during the process of manufacturing the aramid pulp 6, after removing the moisture in the press unit 140, the antistatic agent is treated using a spray method Aramid pulp (6) containing 1.0 wt% of an antistatic agent in a solid content ratio was prepared in the same manner as in Example 1 except that.

The freeness and electrical properties of each of the aramid pulp 6 prepared by Examples, Conventional Examples and Comparative Examples were measured by the following method, and the results are shown in Table 1 below.

Freedom Measurement of Aramid Pulp

The freeness (ml) of the aramid pulp (6) was measured by the Canadian Standard Freeness (CSF) test method of KS M ISO 5267-2.

Friction counter voltage measurement and half-life measurement

NE-7 rotary static tester of Kanebo Engineering Co., Ltd. was used for the KS K 0555 B method, and the frictional voltage was measured as a result of the surface friction cloth. The time taken was measured.

Surface resistance measurement

Concentric ring type tester was used under the conditions of 10V, 20 ℃ and 40% RH based on KS M 3015: 2003.

division Friction band voltage (V) Surface resistance Half-life (seconds) Yeosu-do (ml) Example 1 210 8 × 10 ⁸ 1.5 360 Example 2 190 6 × 10 ⁸ 1.3 350 Example 3 290 5 × 10 ⁹ 2.1 380 Example 4 200 8 × 10 ⁸ 1.5 350 Conventional example 6,000 8 × 10 ¹⁴ 15 540 Comparative Example 1 2,200 5 × 10 ¹² 11 480 Comparative Example 2 200 3 × 10 ⁸ 1.4 540

Since aramid has high insulation resistance, it does not flow the generated static electricity and tends to accumulate. Therefore, the produced aramid pulp 6 easily absorbs dust in the air and gives an electric shock to give anxiety. In addition, since the cohesiveness between the mono fibers is large, the dissociation and beating process does not proceed smoothly, and the degree of freedom does not proceed smoothly.

As can be seen from the results of Table 1 above, when the dissociation and beating process was performed after the antistatic agent was treated, it can be seen that the fibrillation proceeds effectively and shows excellent freeness. On the other hand, if the antistatic agent is treated after the beating process, the antistatic performance is excellent, but it can be seen that the Yeosu Island does not meet the level required by the industry.

In addition, when the antistatic agent is not treated at all, it is understood that not only the degree of freeness is poor, but also the antistatic performance is considerably poor.

Figure 1 is a schematic diagram showing the treatment of the antistatic agent during the aramid filament manufacturing process as an example of the present invention.

Figure 2 is a schematic diagram showing the treatment of the antistatic agent during the aramid pulp manufacturing process as another example of the present invention.

<Explanation of symbols for the main parts of the drawings>

1: short aramid fiber 6: aramid pulp

10: spinneret 20: coagulation unit

30: hand washing 40: antistatic treatment

50: heat treatment unit 60: winder

100: washing unit 110: dissociation unit

120: high resolution 130: grass paper forming portion

140: press part 150: drying part

160: shredding unit 170: packing unit

180: injection nozzle

Claims (6)

In aramid pulp, The frictional electrification voltage is 1,000 V or less, the half life is 1.0 to 2.5 seconds, the surface resistance is 10 ¹⁰ Ω or less, 0.1 to 5% by weight of a carboxylate compound based on the aramid pulp as an antistatic agent, Aramid pulp, characterized in that having a degree of freedom of 300 ~ 500ml. The method of claim 1, The carboxylate compound is an aramid pulp, characterized in that 2,2-thiobisacetic acid bis (2-ethylhexyl) ester [2,2-thiobisacetic acid bis (2-ethylhexyl) ester]. delete delete In the method for producing aramid pulp, Preparing an aramid filament; Imparting a carboxylate compound to the aramid filament for antistatic treatment; Cutting the antistatic treated aramid filament to obtain aramid short fibers; Dispersing the short aramid fibers in water to prepare a slurry; Beating the slurry to form fibrillated aramid short fibers; And A step of making paper from the fibrillated aramid short fibers, The content of the carboxylate compound in the aramid pulp is a method for producing aramid pulp, characterized in that 0.1 to 5% by weight. delete

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