Fiber paper and preparation method therefor

Description

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Chinese patent application No. 202410452155.2 filed on Apr. 16, 2024, the disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND

At present, the aramid paper, used for motor insulation, honeycomb materials and printed circuit board substrates, has a water absorption rate of about 4%. The aramid paper, when used in high humidity or marine environments, can easily incur problems such as poor dimensional stability, unstable insulation and dielectric performances due to hygroscopic and water-absorption properties thereof.

SUMMARY

The disclosure relates to a technical field of papermaking, and in particular to a fiber paper and a method for preparing a fiber paper.

The disclosure provides a fiber paper and a preparation method thereof, which uses a polyarylester fiber as a raw material and utilizes a property of low water absorption rate of the polyarylester fiber to improve problems caused by the fiber paper in a high humidity environment. At the same time, the fiber paper has good uniformity, density, strength and insulation performance.

In a first aspect, a fiber paper is provided according to an embodiment of the disclosure, which includes a first fiber. The first fiber includes a polyarylester fiber which has a diameter of 0.1-3 μm, a length of 0.2-5 mm, and an aspect ratio of 800-1200.

In a second aspect, a preparation method for a fiber paper is further provided according to an embodiment of the disclosure. The fiber paper is the fiber paper described in the first aspect. The preparation method for the fiber paper includes the following:

• • mixing and spinning an island component and a sea component to obtain a sea-island fiber, the island component comprising a polyarylester;
  • removing the sea component in the sea-island fiber to obtain pulps of a polyarylester fiber;
  • papermaking the pulps of the polyarylester fiber to obtain a fiber paper.

The above technical solution provided according to the embodiment of the disclosure has the following advantages compared with some implementations:

In the fiber paper provided according to an embodiment of the disclosure, the polyarylester fiber is used as a raw material and a property of low water absorption rate of which is utilized to improve problems caused by the polyarylester fiber in a high humidity environment. At the same time, a diameter and length of the polyarylester fiber are controlled to meet a specific range, to enable the fiber paper to have better uniformity, density, strength and insulation performance.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute a portion of the specification, illustrate embodiments consistent with the disclosure and, together with the specification, serve to explain the principles of the disclosure.

In order to more clearly illustrate the embodiments of the disclosure or the technical solutions in some implementations, the accompanying drawings needed to be used in the description of the embodiments or some implementations will be briefly introduced below. Obviously, for those skilled in the art, other accompanying drawings can also be obtained based on these accompanying drawing without creative efforts.

FIG. 1 is a schematic flow chart showing a method for preparing a fiber paper according to an embodiment of the disclosure.

DETAILED DESCRIPTION

In order to make purposes, technical solutions and advantages of the embodiments of the disclosure clearer, the technical solutions in the embodiments of the disclosure will be clearly and completely described below in conjunction with the accompanying drawing according to the embodiments of the disclosure. Obviously, the described embodiments are some embodiments of the disclosure, but not all embodiments. Based on the embodiments in the disclosure, all other embodiments obtained by those skilled in the art without any creative efforts fall within the scope of protection sought by the disclosure.

Unless otherwise specified, various raw materials, reagents, instruments and apparatuses used in the disclosure can be purchased from the market or prepared by existing methods.

At present, the aramid paper, used for motor insulation, honeycomb materials and printed circuit board substrates, has a water absorption rate of about 4%. The aramid paper, when used in high humidity or marine environments, can easily incur problems such as poor dimensional stability, unstable insulation and dielectric performances due to a hygroscopic and water-absorption properties thereof.

To solve the above problems, the disclosure intends to use a polyarylester fiber of a water absorption rate of less than 0.1% as a raw material to prepare a fiber paper. The current method for manufacturing a polyarylester fiber starts with liquid crystal polyarylester. Monomer components with specific proportions are used to prepare a raw material suitable for fiberization through acetylation and high-temperature polycondensation, and then a fiber is obtained through melt spinning. The monomer components usually have specific chemical structures and properties to be capable of ensuring a formation of a stable liquid crystal phase during subsequent acetylation and high-temperature polycondensation. A thermal treatment is performed on the obtained fiber to obtain a high-quality polyarylester fiber. If an ordinary melt spinning method is continued, finer polyarylester fiber cannot be obtained, because, as for the liquid crystal polyarylester, a rigid liquid crystal rod-shaped structure is formed inside a fiber, and thus the liquid crystal polyarylester cannot be thinned by subsequent stretching. An orifice of spinneret can only be changed to be smaller to obtain a finer fiber, but a spinning process is extremely unstable, and a portion of the polyarylester fiber with high crystallinity are very easy to clog the orifice of spinneret. Therefore, the current polyarylester fiber generally has a diameter of 5 D per single fiber, which is about 22.5 microns, and a thinnest diameter of a single fiber can be 2.5 D (about 16 microns). However, fibers with such diameter are difficult to be used for papermaking, and must be sheared to be broken to obtain finer fibers for making a pulp. It is well known that the polyarylester fiber is a fiber with higher strength than an aramid and is difficult to break, and thus may cause a great burden and damage to apparatuses. Moreover, a fiber, which is fibrillated and refined in this way, has many split branches and is prone to lumps. In addition, the polyarylester fiber itself needs to be heat treated during production, and a welding and jointing will occur among a portion of the polyarylester fiber, which may lead to the polyarylester fibers being more prone to lumps than other fibers. The lumps reduce a papermaking performance, and result in a paper with a poor uniformity, low strength, non-density and reduced insulation performance. If a repeated pulping and homogenization are carried out to solve the lumps, a large number of fibers will become powder in a later stage, resulting in short fibers to be unable to obtain fine fibers of suitable length. The fibers are not connected enough, resulting in insufficient paper strength.

To this end, the disclosure intends to provide pulps of a melt liquid crystal polyarylester fiber with excellent papermaking performance and strength, and a paper, which is made from the pulps, has an insulation property, chemical resistance and low water absorption, and is particularly suitable for printed circuit boards or the like.

A fiber paper is provided according to an embodiment of the disclosure, which includes

a first fiber. The first fiber includes a polyarylester fiber which has a diameter of 0.1-3 μm, a length of 0.2-5 mm, and an aspect ratio of 800-1200.

As for the fiber paper, the polyarylester fiber is used as a raw material, improving problems thereof incurred in a high humidity environment by utilizing a property of low water absorption rate of the polyarylester fiber. At the same time, a diameter and length of the polyarylester fiber are controlled to meet a specific range, to enable the fiber paper to have better uniformity, density, strength and insulation performance and the like.

Compositions of the polyarylester fiber include a polymer of an aromatic hydroxy carboxylic acid. Alternatively, compositions of the polyarylester fiber include a copolymer of an aromatic hydroxy carboxylic acid, an aromatic dicarboxylic acid, an aromatic diol, and an aliphatic diol. In some embodiments, the compositions of the polyarylester fiber include a polymer consisting only of aromatics. Experiments have shown that a fiber made from the polymer consisting only of the aromatics exhibits excellent physical property and thermal stability. A polymerization formulation for a polyarylester may be a conventionally known method.

Exemplarily, the polyarylester is a polymer polymerized from the aromatic hydroxy carboxylic acid, and specifically a polymer obtained by mixing 70% p-hydroxybenzoic acid (which has a chemical structure as follows:

and 30% p-hydroxynaphthoic acid (which has a chemical structure as follows:

The polyarylester is produced by Nanjing Qingyan polymer new material Co., Ltd and has a model of FS100.

A diameter of the polyarylester fiber is controlled to be 0.1˜3 μm. On the one hand, the diameter of the polyarylester fiber being controlled to be less than 0.1 micron has almost no effect on formatting, and has a large outflow loss during papermaking and a low efficiency, and it is extremely difficult to manufacture or separate pulps with a diameter less than 0.1 micron. On the other hand, for pulps with a diameter larger than 3 microns, the papermaking performance is significantly reduced; a paper strength is reduced; and a texture is also deteriorated, due to a smaller entanglement of the pulps. Therefore, it is preferred to control the diameter of the polyarylester fiber to range from 0.1 to 3 μm in terms of the papermaking performance and paper strength.

The length of the polyarylester fiber is preferably 0.2 to 5 mm, especially 0.5 to 2 mm. If the length of the polyarylester fiber is too short, an entanglement of the polyarylester fiber becomes smaller, resulting in insufficient paper strength, and in turn the pulps is easy to flow out, resulting in greater loss. On the contrary, if the length of the polyarylester fiber is too long, the polyarylester fiber may be entangled into lumps during papermaking, thereby reducing the papermaking performance and may also cause a deteriorated texture of the obtained paper.

An aspect ratio of the polyarylester fiber is 800˜1200, and is selected depending on a dispersion of the polyarylester fiber and a paper strength during paper making.

Excellent paper can be obtained by wet papermaking through using a paper stock containing 5 to 100% by weight of such pulps. There may be a fiber-like matter (a second fiber) other than the polyarylester fiber (a first fiber). The second fiber may be composed of a polyarylester or other polymers. In terms of heat resistance, low moisture absorption and the like, a paper is preferably only composed of the polyarylester. If only the polyarylester fibers are used to make paper, a paper having excellent heat resistance, moisture absorption and adhesiveness performances can be obtained. However, when a higher physical performance such as a tear strength is required, it is preferably to mix in a second fiber for papermaking. In particular, it is preferable to mix in a second fiber produced by a polyarylester via melt spinning.

A diameter of the second fiber is preferably greater than or equal to 8 μm and less than or equal to 30 μm, particularly greater than or equal to 12 μm and less than or equal to 23 μm. If the diameter of the second fiber is too large, a papermaking performance and a compositing performance may not be ideal. If the diameter of the second fiber is too small, a paper strength cannot be increased. The length of the second fiber is suitable to range from 2 to 30 mm, particularly 3 to 8 mm. If the length of the second fiber is too short, a reinforcement effect is small, such that a paper strength may not be greatly improved. If the length of the second fiber is too long, the second fibers may be entangled to be bulk-like during papermaking, resulting in poor papermaking performance. An aspect ratio of the second fiber is preferably 130-500, particularly 250-300. The second fibers are preferably mixed in with a mass proportion of 25-75%.

The polyarylester fibers used in the disclosure are characterized by being non-branched and substantially free of lumps or powders. This kind of polyarylester fiber, since having excellent dispersibility in water, can provide a paper with high papermaking performance, excellent heat resistance, low moisture absorption, excellent paper strength and texture. Moreover, since a particularly dense paper with high air tightness can be obtained through this kind of polyarylester fiber, and a paper suitable as electrical insulating paper can be obtained through this kind of polyarylester fiber.

The polyarylester fibers are obtained by melt spinning a sea-island fiber with a polyarylester serving as an island component and then removing a sea component mainly composed of other polymers. The so-called sea-island fiber refers to a special composition fiber, a cross section of this composition fiber has tens to hundreds of thousands of island components which are island like and exist in a sea component which serve as a substrate. The sea-island fibers are not particularly limited in diameter or cross-sectional shape thereof as long as the sea-island fibers are formed by extrusion and the island components are continuous to a certain extent in an axis direction of fiber. A molecular orientation is easily generated when a shearing is applied to the liquid crystal structure of the polyarylester itself, and thus the island components are likely to be continuous. If the liquid crystal structure of the polyarylester itself is not sheared, relatively long polyarylester fibers can be obtained as compositions of paper pulp. Therefore, even if shearing is performed before the sea components are removed, substantially no powdery matter is generated, and the polyarylester fibers having a substantially constant length can be obtained as compositions of paper pulp. A specific preparation process is as follows.

FIG. 1 is a schematic flow chart showing a method for preparing fiber paper according to an embodiment of the disclosure. As shown in FIG. 1, a method for preparing a fiber paper is further provided according to an embodiment of the disclosure based on a general inventive concept. The fiber paper is the fiber paper described above. The method for preparing the fiber paper includes Step S1-S3.

In Step S1, an island component and a sea component are mixed and spinned to obtain a sea-island fiber, and the island component includes a polyarylester.

The number of islands in the sea-island fiber should preferably ranges from several hundred to several tens of thousands. The number of islands can be changed by adjusting a kneading ratio of two polymers, a spinning temperature, a shear rate, an extrusion-winding ratio and a melt viscosity. In some embodiments, the number of islands can be reduced by increasing a difference in melt viscosity between the sea component and the island component. The polyarylester, when passing through an orifice of spinneret, is subjected to strong action of shearing and stretching, resulting in significant molecular orientation, which causes the polyarylester fibers to exhibit macroscopically higher strength and modulus, while maintains good continuity and homogeneity. During a spinning process, appropriate extrusion-winding ratio usually ranges from 11-60 to help to ensure that the polyarylester fibers are sufficiently stretched and oriented during the spinning process, while a shear speed usually ranges from 1000 to 100,000 (sec-1), to produce a sufficient shear force to orient molecular chains of the polyarylester in the orifice of spinneret while avoiding excessive shear force that could lead to breakage of the polyarylester fibers. A weight ratio of the sea component to the island component is 35:65 to 80:20, preferably 45:55 to 60:40. The higher a proportion of the polyarylester mainly composed of the island component, the higher the economic benefits. However, when a weight of the island component exceeds 65%, the polyarylester mainly composed of the island component are highly susceptible to a variety of factors (e.g. spinning tension, temperature, shear rate, etc.) during the spinning process, resulting in a change in properties of the island component such that the island component may no longer be able to exist effectively as the island component, but is very likely to become the sea component, and thus the polyarylester fiber cannot be obtained.

A polymer used as the sea component preferably includes, but is not limited to, a polyethylene, a polystyrene, a nylon 66, a modified polyester and the like.

In step S2, the sea component in the sea-island fiber is removed to obtain pulps of polyarylester fiber.

The polyarylester has excellent chemical resistance and is not easily degraded or corroded by solvents. With the polyarylester, a wide variety of solvents can be used and pulps with excellent strength can also be obtained. When the polyethylene, polystyrene and nylon 66 are used, it is preferred that a toluene is selected as a solvent which is a lean solvent for the polyarylester and a rich solvent for the polymers (e.g. polyethylene, polystyrene, nylon 66, etc.) which serve as the sea component. If the polystyrene is selected, the polystyrene can be dissolved and removed in a short time at room temperature by selecting the toluene as the solvent.

In a case of selecting the polystyrene, since the toluene or a xylene and the like can be used for treating the polystyrene at room temperature, the polystyrene is particularly preferred in terms of processability and the like. These solvents may be used alone or mixed to be used as a mixed solvent. The disclosure uses a solvent to extract the polymer, and the solvent can be recovered and reused, so as to prepare the pulps in an economical and efficient manner. The fibers, after being treated by the solvent and split, are preferably washed and dried. Another polymer that is particularly preferred as the sea component is the modified polyester, which is easier to be obtained for a preparation of the sea-island fibers. The modified polyester commonly used is a polyester that is extremely easy to be alkali decreased. An alkali-decreased polyester is a polyester composed of a dicarboxylic acid, a hydroxy carboxylic acid, etc., and has alkaline degradability and alkaline solubility. A ratio of an alkali decomposition rate of the alkali-decreased polyester to that of the polyester is preferably more than 1,000, and more preferably more than 3,000. In this way, the sea-island fiber can be subjected to an alkali treatment for a short time. Since the polyarylester since itself has may not be corroded and degraded because of excellent acid and alkali resistance thereof, pulps with excellent performance can be obtained. In addition, since the alkali-decreased polyester can be almost completely removed by treating through an alkaline solution, a heat welding and jointing among fibers does not occur in subsequent conventional heat treatment process.

With respect to the alkali-decreased polyester, it is preferable that constituent units contained in the alkali-decreased polyester are fibers of a dimethyl isophthalate-5-sodium sulfonate and a polyethylene glycol. It has been found through experiments that an alkali decomposition rate of the polyesters containing the above two constituent units is more than 3000 times greater than that of the polyarylester, so the polyesters can be treated with alkaline solutions in a short time. There are requirements for contents of these two constituent units. If the contents of the two constituent units in the polyester are low, an alkali decomposability may be insufficient. When the alkali decomposability is insufficient, a removal time for the polyester is long, which leads to problems such as loss of strength of obtained pulps. On the contrary, if a proportion of these two constituent units is too high, a spinnability will be reduced. For example, if a proportion of the dimethyl isophthalate-5-sodium sulfonate is high, a viscosity will increase, such that a gelation will occur easily, resulting in that an output of a filament is not smooth and the spinnability decreases. On the contrary, if a proportion of the polyethylene glycol increases, the viscosity will decrease, and the filament will break easily. An average degree of polymerization of the polyethylene glycol should be 10 to 100, but more preferably be 20 to 80. When the degree of polymerization is less than 10, an alkali solubility is low. When the degree of polymerization is greater than 100, the alkali solubility is not greatly improved and a degradation may occur.

In other embodiments, other constituent units of carboxylic acids constituting the modified polyester may also include aromatic dicarboxylic acids such as a terephthalic acid, an isophthalic acid and a biphenyl dicarboxylic acid, and aromatic hydroxy carboxylic acids such as a p-methoxybenzoic acid, and aliphatic dicarboxylic acids and the like. These constituent units of carboxylic acids may have various types. In a synthesis of the modified polyester, these constituent units of carboxylic acids can be used as one of the raw materials to esterify with polyols (such as ethylene glycol, propylene glycol and the like) to produce the polyesters with specific properties. It is preferred that 70% or more of total acid composition units constituting the modified polyester are constituent units of the aromatic dicarboxylic acids, particularly constituent units of terephthalic acids.

Since the island component is the polyarylester having excellent alkali resistance, the pulps of the polyarylester fiber having a desired diameter can be obtained, and the diameter is not substantially changed by an alkali treatment. Dissolution, decomposition and removal of a polyester that is easy to be alkali decreased (the sea component) is generally carried out by an impregnation method. The alkaline solution used is preferably a strong alkaline solution such as sodium hydroxide, calcium hydroxide and trisodium phosphate solutions. From a perspective of alkali solubility and corrosiveness of the polyarylester fiber, an alkali treatment is carried out in a treatment solution with a concentration of the alkaline substance of about 2 to 400 g/L, and more preferably in the treatment solution with the concentration of the alkaline substance of about 5 to 20 g/L. If weak alkaline substances such as sodium carbonate, sodium silicate, and sodium dihydrogen phosphate and the like are used, the concentration of the alkaline substance in the treatment solution is 5 to 200 g/L, preferably is 5 to 60 g/L. The treatment solution may include both strong and weak alkali substances, and may also include decomposition accelerators and/or alkali surfactants. Furthermore, an alkali permeation of the polyarylester fiber can be promoted by adding an alkaline surfactant.

A temperature of the alkali treatment is preferably 70° C. to 100° C. When the temperature of the alkali treatment is lower than 70° C., a time required for the alkali treatment becomes longer, whereas when the temperature of the alkali treatment exceeds 100° C., the polyarylester is easily corroded and deteriorated. The polyarylester fiber, after treated with alkali, is neutralized and washed and dried. In addition, since the melt liquid crystal polyarylester has good chemical resistance and alkali resistance, the diameters of the melt liquid crystal polyarylester before and after a removal treatment for the sea component can be considered to be substantially the same, thereby obtaining the pulps of the polyarylester fiber having an arbitrary diameter.

This kind of pulps of the polyarylester fiber is cut into a length of not more than 5 mm, preferably not more than 3 mm, and more preferably 1-2 mm. A cutting can be performed before or after the removal treatment of the sea component, but it is easier to cut with a thicker diameter, so the cutting is best performed before the removal treatment of the sea component. A cutting machine, a pulverizer, or the like can be used for the cutting. A dispersant may also be added into the obtained pulps.

In step S3, the pulps of the polyarylester fiber are papermade to obtain a fiber paper.

The disclosure will be further described below with reference to specific examples. It should be understood that these examples are only used to illustrate the disclosure and are not intended to limit the scope of the disclosure. Experimental methods without specifying specific conditions in the following examples are typically performed in accordance with Chinese national standards. If there is no corresponding Chinese national standards, general international standards, conventional conditions, or conditions recommended by the manufacturer shall be followed.

Example 1

A fiber paper and a method for preparing the fiber paper is as follows.

Preparation of a First Fiber:

A polyarylester used as an island component is a polyarylester with a model of FS100 produced by Nanjing Qingyan polymer new material Co., Ltd, which has a melting point of 280° C., and a viscosity of 30 Pas. An alkali-decreased polyester used as a sea component is obtained by polymerization of a dimethyl isophthalate-5-sodium sulfonate, a polyethylene glycol with a molecular weight of 1500, a terephthalic acid and a glycol ester. An intrinsic viscosity of the alkali-decreased polyester is 0.6. Two specific compositions (the dimethyl isophthalate-5-sodium sulfonate and the polyethylene glycol) account for 15% of a total mass of the polyester, and a molar ratio of the dimethyl isophthalate-5-sodium sulfonate to the polyethylene glycol is 3:7. An alkali dissolution rate ratio of the alkali-decreased polyester and the polyarylester is 5800.

The alkali-decreased polyester and polyarylester are melted and kneaded in a weight ratio of 1:1 through a twin-screw extruder, and introduced into a spinning assembly by a metering pump. A spinning is carried out with a spinning temperature of 310° C., 100 outlet holes, and a spinning speed of 600 m/min to obtain a multifilament of 1000D and a monofilament of 10D. In the multifilament, the numbers of islands is 350.

The multifilament is cut into fibers of about 1.8 mm in length by using a cutting machine, and then immersed in a sodium hydroxide solution with a concentration of 40 g/L at 80° C. for 20 minutes. The fibers, after being rinsed with soapy water, are neutralized with an acetic acid and rinsed with a deionized water for 40 minutes. The obtained pulps of the polyarylester fiber are basically free of branches, and have intact fibers with a length of 1.8 mm, a diameter of 0.1 to 3 microns and an average diameter of 1 micron. The obtained pulps of the polyarylester fiber are basically free of powders or pulps of the polyarylester fiber (i.e., the first fiber) with extremely large fiber diameter.

Preparation of a Second Fiber:

A FS100 polyarylester is used to spin at a spinning temperature of 320° C. and at a spinning speed of 1000 m/min, to obtain a 250D/100f multifilament with a single-filament diameter of 16 um, which is cut into 5 mm short fibers (i.e., the second fiber) by using a chopping machine.

Preparation of a Fiber Paper:

The first fiber and the second fiber are mixed in a mass ratio of 75:25, and then are stirred and dispersed in water, and then pass through a 100-mesh filter for papermaking. The obtained paper is dried in an oven at 150° C., and processed in a calender under conditions of a roller temperature of 250° C. and a linear pressure of 80 kg/cm to obtain a high-performance polyarylester fiber paper with a gram weight of 60 gsm.

Example 2

The mass ratio of the first fiber to the second fiber is changed as 20:80, and rest processes are same as in Example 1.

Example 3

The mass ratio of the first fiber to the second fiber is changed as 50:50, and rest processes are same as in Example 1.

Example 4

The first fiber is used entirely without adding the second fiber, and rest processes are same as in Example 1.

Example 5

The second fiber is used entirely without adding the first fiber, and rest processes are same as in Example 1.

Example 6

The roller temperature of the calender is changed as 280° C., and rest processes are same as in Example 1.

Example 7

The roller temperature of the calender is changed as 220° C., and rest processes are same as in Example 1.

Example 8

The linear pressure of roller of the calender is changed as 120 kg/cm, and rest processes are same as in Example 1.

Example 9

A length of the second fiber which is obtained by being cut in Example 1 is changed as 1 mm, and rest processes are same as in Example 1.

Example 10

A length of the second fiber which is obtained by being cut in Example 1 is changed as 20 mm, and rest processes are same as in Example 1.

Example 11

A length of the sea-island fiber (i.e., the first fiber) which is obtained by being cut in Example 1 is changed as 0.1 mm, and rest processes are same as in Example 1.

Example 12

A length of the sea-island fiber (i.e., the first fiber) which is obtained by being cut in Example 1 is changed as 5 mm, and rest processes are same as in Example 1.

Example 13

The second fiber obtained by spinning in Example 1 is heat treated at 240° C. for 2 hours, 260° C. for 2 hours, and 280° C. for 8 hours under nitrogen protection or under vacuum, and then mixed with the first fiber to make paper, and rest processes are same as in Example 1.

Example 14

The spinning speed for the second fiber in Example 1 is adjusted as 250 m/min to obtain a multifilament of 1000D/100f. A diameter of a single fiber in the multifilament which is chopped is 32 μm, and rest processes are same as in Example 1.

Example 15

The sea component is changed as a polystyrene and then mixed with the FS100 polyarylester at a ratio of 50:50 to obtain a multifilament of 1000D and a monofilament of 10D. In the multifilament, the numbers of islands is 350. The multifilament and monofilament are cut into fibers of about 1.8 mm in length by using a cutting machine, and then immersed in toluene for 90 minutes, rinsed with soapy water, and then rinsed with deionized water for 40 minutes. Obtained first fibers are basically free of branches, and have intact fibers with a length of 1.8 mm, a diameter of 0.1 to 5 microns and an average diameter of 1 micron. The obtained first fibers are basically free of second fibers with powders and extremely large fiber diameter.

Example 16

The second fiber of Example 1 is broken up by a crusher to obtain pulps of polyarylester with fibers of powders and lumps intertwined. This polyarylester fiber is broken in to pieces and have many branches, uneven thickness and a lot of powder. A paper is paper-made from this polyarylester fiber through same papermaking processes as in Example 1. However, a papermaking performance of this polyarylester fiber is poor due to a presence of mixed lumps, such that an obtained paper also has poor texture, multiple gaps, and low insulation property.

Example 17

An alkali-decreased polyester and a polyarylester are added into the extruder, respectively, and then are supplied to a core-sheath composite spinning assembly at a ratio of 1:1 through two groups of meters for spinning at 320° C. Obtained core-sheath composite fibers are also chopped into 1.8 mm, and are sujected to same alkali washing and decomposition process (which utilaizes chemical reactions of the alkaline solution and some compositions in substances to be treated, to achieve a purpose of removing impurities, decomposing pollutants or changing a nature of the substances) as in Example 1 to obtain a polyarylester fiber with a diameter of 10 microns, and then same papermaking and treatment as that of the second fiber in Example 1 are performed on this polyarylester fiber, to obtain a polyarylester fiber paper.

Comparative Example 1

DuPon Monex aramid paper is used.

Parameters of various Examples and Comparative Examples are shown in the following table:

			Mixing						diameter	average
			ratio of			Length	Length	heat	of	diameter
			first and	Roller	linear	of second	of first	treatment	second	of first
	Sea	Island	second	temperature	pressure	fiber	fiber	of second	fiber	fiber
	component	component	fibers	° C.	kg/cm	mm	mm	fiber	μm	μm

Example 1	alkali-decreased	polyarylester	75:25	250	80	5	1.8	\	16	1
	polyester
Example 2	alkali-decreased	polyarylester	20:80	250	80	5	1.8	\	16	1
	polyester
Example 3	alkali-decreased	polyarylester	50:50	250	80	5	1.8	\	16	1
	polyester
Example 4	alkali-decreased	polyarylester	100	250	80	\	1.8	\	\	1
	polyester
Example 5	alkali-decreased	polyarylester	0	250	80	5	\	\	16	\
	polyester
Example 6	alkali-decreased	polyarylester	75:25	280	80	5	1.8	\	16	1
	polyester
Example 7	alkali-decreased	polyarylester	75:25	220	80	5	1.8	\	16	1
	polyester
Example 8	alkali-decreased	polyarylester	75:25	250	120	5	1.8	\	16	1
	polyester
Example 9	alkali-decreased	polyarylester	75:25	250	80	1	1.8	\	16	1
	polyester
Example 10	alkali-decreased	polyarylester	75:25	250	80	20	1.8	\	16	1
	polyester
Example 11	alkali-decreased	polyarylester	75:25	250	80	5	0.1	\	16	1
	polyester
Example 12	alkali-decreased	polyarylester	75:25	250	80	5	5	\	16	1
	polyester
Example 13	alkali-decreased	polyarylester	75:25	250	80	5	1.8	being heat	16	1
	polyester							treated
Example 14	alkali-decreased	polyarylester	75:25	250	80	5	1.8	\	32	1
	polyester
Example 15	polystyrene	polyarylester	75:25	250	80	5	1.8	\	16	1
Example 16	\	\	75:25	250	80	5	\	\	16	\
Example 17	\	\	75:25	250	80	5	1.8	\	16	10

Comparative

DuPont Meta-Aramid Paper

Example 1

The fiber papers provided in the Examples and Comparative Examples are tested for dielectric strength, tensile strength, elongation, and moisture absorption. The results are shown in the following table:

		Di-
		electric	Tensile	Moisture
	Weight	strength	strength	absorp-
	gsm	kV/mm	N/cm	tion %	Remarks

Example 1	60	20	45	0.1	/
Example 2	60	16	40	0.1	/
Example 3	60	18	46	0.1	/
Example 4	60	21	37	0.1	/
Example 5	60	4	10	0.1	/
Example 6	60	24	50	0.1	/
Example 7	60	16	36	0.1	/
Example 8	60	22	46	0.1	/
Example 9	60	18	40	0.1	There are defects
					in the papermaking
Example	60	17	43	0.1	There are defects
10					in the papermaking
Example	60	16	38	0.1	There are defects
11					in the papermaking
Example	60	15	35	0.1	There are defects
12					in the papermaking
Example	60	19	60	0.1	/
13
Example	60	16	37	0.1	There are defects
14					in the papermaking
Example	60	18	45	0.1	/
15
Example	60	14	43	0.1	The papermaking is
16					extremely difficult
					to be performed
Example	60	12	23	0.1	The papermaking is
17					extremely difficult
					to be performed
Compar-	60	19	48	5	/
ative
Example 1

It can be seen from the above table that the fiber paper prepared by the method provided according to an embodiment of the disclosure has excellent insulation performance, low moisture absorption, and strong tensile strength.

Various embodiments of the disclosure may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and simplicity and should not be understood as a hard limit to the scope of the disclosure; therefore, the described range should be considered to have specifically disclosed all possible subranges as well as the single values within such a range. For example, a description of a range from 1 to 6 should be considered to have specifically disclosed subranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, and from 3 to 6, and a single number within the stated range, such as 1, 2, 3, 4, 5, and 6, which applies regardless of the range. Additionally, whenever a numerical range is indicated herein, it is intended to include any cited number (fractional or whole) within the indicated range.

In the disclosure, unless otherwise specified, the directional words used such as “upper” and “lower” refer specifically to the direction of the figure in the drawing. In addition, in the description for specification of the disclosure, the terms “including”, “comprising”, etc. indicate “including but not limited to”. In this document, relational terms such as “first” and “second” are merely used to distinguish one entity or operation from another and do not necessarily require or imply any such actual relationship or sequence between these entities or operations. In the disclosure, “and/or” describes the relationship between associated objects, indicating that there may be three relationships. For example, A and/or B may refer to: A alone, both A and B, and B alone. A and B can be singular or plural. In this document, “at least one” means one or more, and “plurality” means two or more. “At least one”, “at least one of the following” or similar expressions thereof refers to any combination of these items, including single items or any combination of plural items. For example, “at least one of a, b, or c”, or “at least one of a, b, and c” may represent: a, b, c, a˜b (that is, a and b), a˜c, b˜c, or a˜b˜c in which a, b, and c can each be single or multiple.

The above descriptions are only specific embodiments of the disclosure, enabling those skilled in the art to understand or implement the disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principle defined herein may be practiced in other embodiments without departing from the spirit or scope of the disclosure. Therefore, the disclosure is not to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features claimed herein.