JPH07157919A - Method for spinning polybenzazole fiber at high speed - Google Patents

Abstract

PURPOSE:To produce filament having a fine single filament size at a high speed by extruding a liquid crystalline dope of a polybenzazole from a spinneret having a high hole density, drawing the resultant yarn in an air gap in a gas stream at a temperature within a specific range and then desolvating the yarn in a coagulation bath. CONSTITUTION:This method for spinning polybenzazole fiber at a high speed is to extrude a liquid crystalline dope of a lyotropic polybenzazole composed of polybenzoxazole, polybenzothiazole or a copolymer thereof and a polyphosphoric acid solvent from a spinneret having at least 20 holes/cm<2> hole density at >=200 deg.C temperature, then draw the resultant yarn in an air gap region in a gas stream at 50-100 deg.C, subsequently introduce the yarn into a coagulation water bath, desolvate the yarn, drain water with an air knife, pass the yarn through heated godet rollers and dry the yarn. Thereby, the filament yarn having a fine size of <=20mum average single filament diameter is stably produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing fibers made of polybenzoxazole or polybenzthiazole polymer with excellent productivity.

[0002]

2. Description of the Related Art Polybenzoxazole and polybenzthiazole polymers having lyotropic liquid crystallinity do not show thermoplasticity. These are fiberized by the dry jet wet spinning method. That is, a method in which a dope containing a polybenzazole polymer and an acid solvent is extruded from a spinneret, stretched in an air gap, diluted with a solvent, and brought into contact with a non-solvent that does not dissolve the polymer to coagulate. 1 fiber was obtained from this process
It can converge to a book or multiple books of various sizes.

It is preferable to build many filaments in a short time and at high speed. Further, it is preferable to reduce the occupied area of each filament to make continuous fibers having a small number of fineness, rather than making a small number of fibers having a large fineness. However, yarn breakage is likely to occur in spinning with a small single yarn denier. Especially at high speeds and with many holes in the spinneret, yarn breakage frequently occurs during spinning. Even under such conditions, it is desired to reduce single yarn breakage as much as possible.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a method for stably producing a filament having a small single yarn fineness at a high speed even under the condition of a high pore density.

[0005]

That is, according to the present invention, a plurality of filaments are spun from a liquid crystal dope composed of a solvent and polybenzoxazole, or polybenzthiazole or a polybenzazole polymer which is a copolymer of these. In the method for producing a fiber, (1) a spinning dope is extruded from a plurality of holes of a spinneret having a hole density of at least 2.0 holes / cm ² at a temperature of 100 ° C. or higher to form a plurality of dope filaments, 2) This dope
The filament is stretched in a gas air gap under the conditions of an air flow capable of uniformly cooling the filament at 50-100 ° C., and (3) the stretched dope filament is brought into contact with a liquid to desolvate the filament. The manufacturing method comprises the steps of.

The second technique of the present invention is a polybenzazole fiber having an average single fiber diameter of about 21 μm or less, which is obtained by the above manufacturing process. Further, the above-mentioned production method, wherein the dope filament is converged into one or more before, during, or after contact with the cleaning liquid. Air velocity in the air gap is at least 0.05m
/ Sec or more, the above-mentioned manufacturing method. The above manufacturing method, wherein the air velocity in the air gap is at least 0.1 m / sec or more.
The above-mentioned manufacturing method, wherein the air velocity in the air gap is at least 0.5 m / sec or more. Polybenzazole fiber having an average single fiber diameter of about 18 μm or less produced by the above production method. The above polybenzazole fiber, wherein the polybenzazole is polybenzoxazole.

When many polybenzazole filaments are densely packed and spun at high temperature, the outer filaments cool faster than the inner filaments. This difference in temperature is not optimal for filaments located inside when it is optimal for filaments located outside, and vice versa. By creating an air flow in the air gap, the same atmospheric temperature history can be given to all fibers. The yarn breakage can be minimized by controlling the ambient temperature. Further, by creating an air flow in the air gap, it is possible to obtain an effect that the filaments become more uniform.

The present invention relates to a lyotropic liquid crystalline polybenzazole polymer, namely polybenzoxazole,
A spinning stock solution containing polybenzothiazole or a copolymer thereof is used. The polybenzazole polymer used here is the "Liquid Crystalline" by Wolfe et al.
Polymer Compositions, Process and Products '' USPat
ent 4,703,103 (October 27,1987); Wolfe et al., `` Liquid
Crystalline Polymer Compositions, Process and Produc
ts '' US Patent 4,533,692 (August 6,1985); Wolfe et al., `` Liquid Crystalline Poly (2,6-Benzothiazole) Compo
sitions, Process and Products '' US Patent 4,533,7
24 (August 6,1985); Wolfe et al., "Liquid Crys talline.
Polymer Compositions, Process and Products '' USPat
ent 4,533,693 (August 6,1985); Evers `` Thermoxdative
ly Stable Articulated p-Benzobisoxazole p-Benzobis
thiazole Polymers '' US Patent 4,359,567 (November 1
6, 1982); Tsai et al. `` Method for Making Heterocyclic
Block Copolymer Compositions, Process and Products ''
USPatent 4,578,432 (March 25,1986); 11 Ency.Poly.
Sci. & Eng., `` Polybenzothiazoles and Polybenzoxazo
and Polybenzoxazoles 」, 601 (J. Wiley & Sons 1988) an
d WW Adams et al., "The Materials Science", 601 (J. Wiley
& Sons 1988) and WWAdams et al. `` The Materials Scien
ce and Engineering of Rigid-Rod Polymers '' (Materia
ls Research Society 1989)
Random, sequential, block copolymers of BO, PBT and PBO, PBT.

The polymer may be AB type units as represented by chemical structural formula 1 (a) and / or AA / BB type units as represented by chemical structural formula 1 (b).

[0010]

[Chemical 1]

Here, each Ar represents an aromatic group selected from the polymers of lyotropic liquid crystal polymer (ie, forming a liquid crystal domain above the critical concentration point) polybenzazole, wherein the aromatic group is a pyridinylene group. Such a hetero ring may be formed, but it is preferable that a ring is formed by carbon.The aromatic group may be a condensed polycyclic group ring or a non-condensed polycyclic group, provided that A 6-membered ring is preferred, though the size is not limited, but the aromatic group preferably contains 18 or less carbon atoms, and more preferably 12
It preferably contains not more than 6 carbon atoms, more preferably not more than 6 carbon atoms. AA / BB
Arl of the mold unit preferably has a 1,2,4,5-phenylene structure or an analogue thereof. AB type unit Ar
Preferably has a 1,3,4-phenylene structure or an analogue thereof. Each Z is independently an enzyme atom or a sulfur atom. Each DM is a divalent organic structure selected from polybenzazoles which are directly bonded or lyotropic liquid crystal polymers independently of each other. As the divalent structural unit, the aromatic group (Ar) described above is used.
Is preferred. Particularly, a 1,4-phenylene structure or its analog is preferable. The nitrogen atom and Z structure of each azole ring are bonded to the carbon atom of the adjacent aromatic group to form a condensed form of the 5-membered azole ring and the aromatic group. AA
The azole ring of the / BB type unit is 11 Ency. Po in the cited document.
ly.Sci. & Eng., `` Polybenzothiazoles and Polybenzole
s ", 601 (J. Wiley & Sons 1988).

The polymer is preferably composed of AB-PBZ repeating units or AA / BBZ repeating units, more preferably essentially of AA / BB-PBZ repeating units. The azole ring in the polymer is preferably an oxazole ring in which Z is an oxygen atom.

The repeating unit used in the present invention has the structural formula 2
Those shown in (a)-(h) are preferable. Those represented by Structural Formulas 2 (a)-(f) are more preferable, and those represented by Structural Formulas 2 (a)-(d) are more preferable.

[0014]

[Chemical 2]

[0015]

[Chemical 3]

Each polymer preferably has at least about 25 or more repeating units on average, more preferably at least about 50 or more repeating units, still more preferably at least about 1 repeating unit.
It is preferable to have a repeating unit of 00 or more. AA /
The intrinsic viscosity of the BB-PBZ rigid linear chain is preferably at least about 10 dl / g or more, more preferably at least about 15 as measured by methanesulfonic acid at 25 ° C.
It is preferably dl / g or more, more preferably at least about 20 dl / g or more. For some applications, the intrinsic viscosity is optimally at least about 25 or 30 dl / g. The intrinsic viscosity is 60
It may be dl / g, but is preferably 40 dl / g.
The intrinsic viscosity of the semi-rigid AB-PBZ polymer is preferably at least about 5 dl / g, more preferably at least about 10 dl / g, and even more preferably at least about 15 dl / g. Something is preferable.

This polymer or copolymer is dissolved in a solvent to prepare a solution or dope. Polybenzoxazole and polybenzothiazole can be dissolved in cresol,
It is preferable to use a soluble acid as the solvent. The acid has a good non-oxidizing property. As an example of a preferable solvent, polyphosphoric acid,
Methane sulfonic acid, sulfuric acid and mixtures thereof may be mentioned. More preferably, the acid is polyphosphoric acid and / or methanesulfonic acid. Polyphosphoric acid is more preferable.

The dope should contain a sufficient concentration of polymer to form the liquid crystal domains of the dope. Preferably, the polymer concentration is at least about 7 weight percent or greater, more preferably at least about 10 weight percent or greater, and even more preferably at least about 14 weight percent or greater. Maximum polymer concentration is primarily constrained by workability such as polymer solubility and dope viscosity. Rarely dopes with a polymer concentration of 30 weight percent are used, and typically 20 weight percent or less are used.

The polymer or copolymer and dope suitable for the present invention are synthesized by the following known methods.
As a synthesis method, US Patent 4,533,693 (A of Wolfe et al.
ugust 6,1985); Sybert et al., US Patent 4,772,678 (Septe.
mber 20,1988); Harris US Patent 4,847,350 (July 1)
1,1989); Gregory's US Patent 5,089,591 (February 18,
1992); “An Integrated Laboratory Proc by Ledbetter et al.
ess for Preparing Rigid Rod Fibers from Monomaer
s ”“ The Materials Science and Engineering of Rigid
-Rod Polymers, pp. 253-264 (Materials Resea
rch Society 1989). In short, appropriate AA type and BB type or AB type monomers in a non-oxidizing, non-dehydrating acid solvent in a non-oxygen atmosphere while vigorously stirring at a high shear rate, the temperature is from 120 ° C or lower. The reaction is carried out while raising the temperature by stepwise or lamp control to at least about 190 ° C. Examples of AA type monomers include terephthalic acid and analogs thereof. Examples of BB type monomers include 4,6-diaminoresorcinol, 2,5 diaminohydroquinone, 2,5-diamino-1,4-dithiobenzene, and analogs thereof, which are stored primarily as acid salts. Examples of AB type monomers include 3-amino-4-hydroxybenzic acid, 3-hydroxy-4-aminobenzic acid and analogs thereof, which are mainly stored as acid salts.

In order to carry out spinning with the highest productivity, it is important that the dope has high uniformity and contains no bubbles or solid particles. These are achieved by a combination of many known methods below, but the present invention is not limited by the following methods. It is possible to use a wire mesh or / and a silica sand layer for filtering foreign substances, metal scraped particles or particles, a shear layer such as a glass layer, a sintered ceramic or a sintered metal. A single-screw, twin-screw extruder, static mixer and thus a mixing device can be used to further improve the uniformity of the dope.

The dope is spun through a spinneret having a plurality of holes. Pore density of the spinneret must be at least about 1.0 / cm ² or more, more preferably 2.0 pieces / cm ² or more, more preferably at least about 3.0 / cm ² or more is good. Each of the holes in the spinneret may be any desired size, but the average diameter at the point where the dope leaves the spinneret is 0.
It is preferably 5 mm or less, more preferably 0.4 mm or less, still more preferably 0.35 mm or less. The hole arrangement may be any arrangement, but a circumferential arrangement or a lattice arrangement is preferred.

The dope is extruded from the spinneret at 100 ° C. or higher. The spinning temperature is preferably about 120 ° C or higher, more preferably 140 ° C or higher. The upper limit of spinning temperature is determined by the stability of the dope. The spinning temperature is at most about 220 ° C. or less, more preferably about 200 ° C.
The following are preferred. The optimum discharge amount depends on the size and shape of the spinneret, the dope characteristics, and other conditions.

The dope is extruded from the spinneret and enters the void between the spinneret and the solidification zone. This void is commonly referred to as the "air gap" but does not require air. The air gap may contain anything that does not affect or interfere with coagulation, such as air, nitrogen,
It may be something like argon, helium, carbon dioxide. The air gap contains a draw zone for stretching the dope. The spin draw ratio is defined as the ratio of the filament take-up speed to the average flow velocity of the dope capillary. This spin draw ratio is at least about 10 or more, preferably at least about 20 or more,
More preferably, it is at least about 40 or more, more preferably at least about 50 or more, and even more preferably at least about 63 or more. The length of the air gap is usually 5 cm or more and 100 cm or less, but it can be shorter or longer than this range as required.

The temperature of the air gap is about 50 ° C. or higher,
It is preferably about 100 ° C or lower. More preferable temperature is 6
Between 0 ° C and 90 ° C. The gas serves to cool the dope before it contacts the wash liquor. If the temperature of the air gap is less than about 50 ° C., the cooling is too rapid, which is not preferable. If cooling is too rapid, the spinning tension will be too high and spinning will be unstable. It is considered that this is because the extensional viscosity of the dope has a very high temperature dependency. If the temperature of the air gap is higher than about 100 ° C, it is considered that a draw resonance-like instability phenomenon occurs.

The cooling gas in the air gap flows at a flow velocity sufficient to uniformly cool the dope filament. This causes all filaments to receive approximately the same cooling history. The gas flow rate is 0.02 m / sec to 1.
The range is preferably 0 m / sec, more preferably 0.05 m.
/ Sec to 0.9 m / sec. More preferably 0.75
It is from m / sec to 0.8 m / sec. The air flow is preferably orthogonal to the moving direction of filament in the air gap.

After the dope filament is stretched, it is washed by diluting the solvent and catalyzing it with an air flow that is insoluble in the polybenzazole polymer. This desolvation process is usually called coagulation in the initial stage, and the subsequent process of removing most of the solvent is called washing. The fluid may be a gas such as water vapor, but is preferably a liquid and more preferably an aqueous solution. The fibers may be contacted with the liquid in a bath or spray. The liquid bath is JP-A-6
3-12710; JP-A-51-35716; JP-B-44
Various forms incorporated into -22204 may be used. Also, for example, Guertin's USPatent5,034,250 (J
A combination of two roller spraying methods as described in Uly 23, 1991) may be used while the fibers are running. The washed fibers preferably contain less than 2% acid, more preferably less than 0.5%. It is more preferably 0.1% or less.

The filaments obtained in this step are bundled into fiber bundles having one or more different finenesses. This bundling step may be performed before, during or after the coagulation / water washing step. A fiber composed of only one filament is called a monofilament fiber, and a fiber composed of a plurality of filaments is called a multifilament fiber.
A fiber tow is "a bundle of large continuous fibers that are not twisted clearly but are bundled loosely and formed into a rod shape, usually assembled by crimping." (Dictionar
y of Fiber & Textile Technology, 1990 Hoechst Celan
ese)

The fibers coagulated and washed with water are collected and dried by a known method. Further, if necessary, heat treatment can be performed to increase the tensile elastic modulus. A spinning oil may be added.

The fibers can be produced at high speed. The spinning speed is defined by the yarn speed at the exit of the coagulation / water washing process. The yarn speed is preferably at least about 75 m / min, more preferably about 100 m / min, even more preferably about 2
00m / min or more is good. In addition, 400m / min, 600m
Spinning at speeds per minute or higher is also possible.

The single yarn diameter of the finished yarn is preferably 21 μm or less, more preferably 19 μm or less, and further preferably 1
5 μm or less is preferable. The filament diameter and the minimum value of single yarn denier are practically limited. The average filament diameter of each filament is 8 μm, and the filament fineness at this time can be 0.7 dpf. The average tensile strength is preferably 1.38 GPa (200 kpsi) or more, more preferably 2.76 GPa (400 kpsi).
The above is preferable, and more preferably 4.14 GPa (60
0 kpsi) or higher is preferred, most preferably 5.48
GPa (800 kpsi) or more is preferable. Average tensile modulus after heat treatment is 241 GPa (35 mpsi)
The above is preferable, and more preferably 290 GPa (42 m
psi) or higher is preferable. The tensile modulus of the fiber before heat treatment is usually lower (approximately half) than that of the fiber after heat treatment.

The present invention can improve the stability when spinning a large number of dense filaments at the same time.
According to the present invention, yarn breakage during spinning can be effectively minimized. Furthermore, the fineness unevenness between fibers can be reduced.

[0032]

The following examples are for purposes of illustration only, and are not limiting on either the specification or the claims of the present invention. All quantities and percentages are by weight unless otherwise noted.

Examples 1 to 4 and Comparative Examples 1 to 7 A polyphosphoric acid solution prepared by dissolving 14% by weight of a cis-polybenzoxazole polymer having an intrinsic viscosity of 30 dl / g is shown in Table 1.
It was extruded from the spinneret kept at 160 ° C. under the conditions shown in. The extruded filament was coagulated with ion-exchanged water at room temperature, and this yarn was introduced to 5 rollers and washed with water. Further, the yarn, which had been drained with an air knife, was passed through a series of godet rolls where the temperature was successively increased, and dried. Table 1 shows the spinning conditions and the physical properties of the fibers. From the table, it is understood that the yarn breakage during spinning frequently occurs when the condition of the invention falls outside the scope of the claims. In the table, the unit of stress is described in grams / denier (g / d), but in order to convert to kpsi, 1 g / d should be multiplied by 20.48.

[0034]

[Table 1]

[0035]

According to the present invention, a polybenzazole multifilament having a fineness and a large filament right can be stably produced at a high speed.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Stephen Rosenberg 48640 Midland Rosemary Court, Michigan, USA 25 (72) Inventor Ashishen 48642 Midland Burning Bushrain 210, Inventor Timothy L Ferry United States Michigan 48640 Midland Woodbury Court 5803 (72) Inventor Chi Chun Chau United States Michigan 48640 Midland Bluebird Drive 4205 (72) Inventor Miyana Serrano United States Michigan 48640 Midland Nacoma Drive 605

Claims (2)

[Claims] 1. A method for producing a fiber in which a plurality of filaments are spun from a liquid crystalline dope composed of a solvent and polybenzoxazole, or polybenzthiazole or polybenzazole polymer which is a copolymer of these, A method of manufacturing. (1) A dope filament is formed by extruding a spinning dope at a temperature of 100 ° C. or higher from a plurality of holes of a spinneret having a hole density of at least 2.0 holes / cm ² , (2) this dope filament The filament is stretched in a gas air gap under the conditions of an air flow capable of uniformly cooling the filament at 50-100 ° C,
(3) The stretched dope filament is brought into contact with a liquid to remove the solvent from the filament. 2. A polybenzazole fiber having an average single fiber diameter of about 21 μm or less, which is produced by the production method according to claim 1.