JPH0827622A - Polybenzazole monofilament and its production - Google Patents

Abstract

PURPOSE:To provide a polybenzazole monofilament excellent in mechanical propertiesand 1ightweightness, having a high thermal stability and useful for a high-modulus wire material by spinning a dope composed of an acid solvent and a polybenzazole polymer under a specified condition. CONSTITUTION:A dope composed of an acid solvent and polybenzazole polymer and having >=7wt.% polymer concentration is discharged through a spinning nozzle 1 and the discharged dope filament 2 is cooled to a temperature of <=the solidification temperature of the dope by using a quenching unit 3. The dope filament is allowed to pass through a coolung roll 4 and a coagulation bath 5 and stretched by >=about 0.15% while removing a large part of the acid solvent by a water-washing roll 6 and a water-washing spray nozzle 7. After it is washed in a waterwashing bath 9, it is dried, thus producing the objective poly-benzazole monofilament having >=15dpf single yarn fineness and >=700g/d initial elasticity modulus.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polybenzazole monofilament which is useful for a lightweight and high elastic modulus wire having high thermal stability. The polybenzazole wire can be used as a net, a screen, a brush, a gut, a tension member, a rubber reinforcing material, and other general industrial materials.

[0002]

The lyotropic liquid crystalline polybenzoxazole and polybenzthiazole polymers do not exhibit thermoplasticity. These are fiberized by the dry jet wet spinning method as shown in Japanese Patent Publication No. 63-500529. 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.

However, until now, research has been carried out in consideration of the high strength and high modulus of elasticity of the polybenzazole fiber, so that no attempt has been made on the performance and manufacturing method of the polybenzazole wire. Therefore, there was a technique for producing a fiber having a single yarn fineness of at most 10 dpf or less, but a polybenzazole fiber having a good fiber morphology and mechanical properties of 15 dpf or more capable of exhibiting sufficient bending hardness and abrasion resistance as a wire rod. Is not known about.

[0004]

The present invention aims to provide polybenzazole monofilaments having excellent mechanical properties and a method for producing them.

[0005]

That is, the present invention provides a polybenzazole monofilament having a single yarn fineness of 15 dpf or more and an initial elastic modulus of 700 g / d or more. And a method for producing a polybenzazole monofilament having a single yarn denier of 15 dpf or more from a dope composed of an acid solvent and a polybenzazole polymer,
A method for producing a polybenzazole monofilament, which comprises the following steps. (1) A dope having a polymer concentration of 7 wt% or more is extruded from a die to form a dope filament, and (2) the dope filament is brought into contact with a non-solidifying fluid or a cooling solid to cool it to a temperature below the solidification temperature of the dope, and then ( 3) Remove most of the acid solvent while applying a draw of approximately 0.15% or more, and then dry. (4) Dry the washed fiment. Is.

As the polybenzazole polymer of the present invention, a spinning stock solution containing a lyotropic liquid crystalline polybenzazole polymer, that is, polybenzoxazole, polybenzothiazole or a copolymer thereof is used. The polybenzazole polymer used here is Wo
lfe et al., "Liquid Crystalline Polymer Compositions,
Process and Products '' US Patent 4,703,103 (October
27,1987); "Liquid Crystalline Polymer" by Wolfe et al.
Compositions, Process and Products '' US Patent 4,5
33,692 (August 6,1985) ； Wolfe et al., “Liquid Crystal
line Poly (2,6-Benzothiazole) Compositions, Process
and Products '' US Patent 4,533,724 (August 6,1985)
; Wolfe et al., "Liquid Crystalline Polymer Composit
ions, Process and Products '' US Patent 4,533,693 (Au
gust 6,1985) ； Evers “Thermoxdatively Stable Arti
culated p-Benzobisoxazole p-Benzobisthiazole Polym
ers ”US Patent 4,359,567 (November 16,1982); Tsai
`` Method for Making Heterocyclic Block Copolym
er Compositions, Process and Products '' US Patent 4,
578,432 (March 25,1986) ； 11 Ency.Poly.Sci. & Eng.,
`` Polybenzothiazoles and Polybenzoxazoles '', 601 (J.
Wiley & Sons 1988) and WWAdams et al., `` The Materials
Science and Engineering of Rigid-Rod Polymers '' (Ma
Random PBO, PBT and PBO, PBT, as described in (2).
Sequential, block copolymer.

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

[0008]

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Here, each Ar represents an aromatic group selected from polylyzazole polymers which are lyotropic liquid crystal polymers (ie, which form a liquid crystal domain above the "critical concentration point"). The aromatic groups are like pyridinylene groups. Heterocycle, but preferably forms a ring with carbon.The aromatic group may be a condensed polycyclic group ring or a non-condensed polycyclic group, provided that one 6 A member ring is preferred, although the size is not limited, but the aromatic group preferably contains 18 or less carbon atoms, more preferably 12 carbon atoms.
It preferably contains not more than 6 carbon atoms, more preferably not more than 6 carbon atoms. AA / BB
Ar1 of the mold unit preferably has a 1,2,4,5-phenylene structure or an analogue thereof. Ar of the AB type unit preferably has a 1,3,4-phenylene structure or an analog thereof.
Each Z is independently an oxygen 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 above-mentioned aromatic group (Ar) is preferable. In particular,
A 1,4-phenylene structure or its analogue is preferred.
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. The azole ring of the AA / BB type unit is described in 11 Ency.Poly.Sci. & Eng., “Polybe.
nzothiazoles and Polybenzoxazoles '', 601 (J. Wiley &
Sons 1988) may be either cis type or trans type.

The polymer is preferably composed of AB-PBZ repeating units or AA / BB-PBZ repeating units, more preferably essentially 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. The one represented by Structural Formula 2 (a)-(f) is more preferable, and the one represented by Structural Formula 2 (a)-(d) is more preferable.

[0012]

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[0013]

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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 (Sep
tember 20,1988); Harris US Patent 4,847,350 (Jul
y 11,1989); US Patent 5,089,591 (Februar of Gregory
y 18,1992); “An Integrated Laborato by Ledbetter et al.
ry Process for Preparing Rigid Rod Fibers from Mon
omaers "" The Materials Science and Engineering o
f Rigid-Rod Polymers, pp. 253-64 (Materials Researc
h 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 mainly stored as acid salts. . Examples of AB type monomers are 3-amino-4-hydroxybenzoic acid, 3-hydroxy-4-aminobenzoic acid, 3-amino-4-tribenzic acid, 3-amino-4-hydroxybenzoic acid, which are mainly stored as acid salts.
Thio-4-aminobenzic acid and analogs thereof.

In the present invention, a lyotropic liquid crystalline polybenzazole polymer solution is used, but the third component can be added at the solution preparation stage or the solidification stage. As the third component, inorganic particles such as metal and ceramics and filler or polyamide. , Epoxy and other resins, dyes and the like can be used. It is desirable that 90% or more by weight of the polybenzazole wire is polybenzazole in order to exhibit excellent mechanical properties. The polybenzazole polymer may contain a small amount of residual solvent or a salt thereof. The amount of these components is preferably 5% or less by weight, and can be reduced to 1% or less by performing sufficient extraction in the manufacturing process, but from the viewpoint of productivity, it is sufficient to be about 3% or less. An acid is mainly used as the residual solvent, but it is preferable to carry out a neutralization treatment before leading to the drying step. The neutralization process is
It can be carried out by contacting with an alkaline solution containing alkali metal or alkaline earth metal ions such as potassium or sodium or an aqueous ammonia solution, and then washing excess alkali with water.

The cross-sectional area of the wire is preferably 0.0025 mm ² or more in order to exert sufficient strength and tensile resistance of the single fiber. Especially, it is important for improving bending hardness. By improving the bending hardness of the single fiber, it becomes possible to maintain a shape suitable as a reinforcing material for plastic or rubber without twisting a large number of fibers together. The cross-sectional shape of the wire rod of the present invention may be a perfect circle, an ellipse, or a polygon. Since polybenzazole wire cannot be easily cut, it is difficult to accurately determine the cross-sectional area, so the cross-sectional area is represented by the linear density (denier). The density of the polybenzazole wire is 1.55 g / cm ² ,
The linear density with a cross-sectional area of 0.0025 mm ² calculated from this is 15 denier. The higher the linear density of the wire, the wider the application will be. However, in the case of a very thick polybenzazole wire, the disorder of the molecular orientation in the solidification step becomes large and the elastic modulus tends to decrease. In order to exhibit a sufficient elastic modulus, 2000 denier or less is preferable, and 50 is more preferable.
It is preferably 0 denier or less, more preferably 150 denier or less.

Higher modulus of polybenzazole wire is desired, but 200 GP obtained with high strength steel
It is difficult to exceed a in the case where the number of single fibers is 15 denier or more. However, the specific gravity of polybenzazole wire is less than one fifth of that of steel, so 100 GP
Even with a (about 700 g / d), a reinforcing effect more than double the weight can be obtained. Therefore, it is extremely important to provide a wire rod having a weight of 700 g / d or more, more preferably 1000 g / d or more, and most preferably 1400 g / d or more in order to reduce the weight of the wire and the composite material using the wire. .

A typical manufacturing process of the polybenzazole wire is as follows.

The dope is extruded from the die to form a dope filament. At this time, the opening area of the die is selected so that the ratio of the wire drawing speed to the dope discharge linear speed is about 8: 1 to about 70: 1. If the draw ratio when forming this dope is less than about 8, the molecular orientation of the dope filament becomes insufficient and the elastic modulus of the wire decreases. On the other hand, if it exceeds about 70, the unstable phenomenon of extensional flow tends to occur, and the diameter variation of the completed wire may become remarkable. The preferred draw ratio in forming the dope filament is approximately 12 to 40.
The temperature at which the dope is discharged from the spinneret affects the flow stability in the spinneret and the tension generated during extensional flow.
The optimum temperature largely depends on the polymer concentration of the dope and the degree of polymerization of polybenzazole. A preferable dope discharge temperature is, for example, 130 ° C to 180 ° C.

The dope filament is brought into contact with a non-solidifying fluid or with a chilled solid to cool it below the solidification temperature of the dope and then to the solidification step of extracting the solvent. The solidification temperature of the dope depends on the kind of the solvent, but is about 85 ° C. in the case of the polyphosphoric acid solvent. If solidification is started before the dope is sufficiently cooled, solidification proceeds rapidly, so that the molecular orientation advanced by stretching is largely disturbed. It is considered that this is because the polybenzazole polymer is significantly relaxed due to the relaxation of the solvent molecules that occupy most of the dope. For cooling the dope filament, air or liquid at room temperature or gaseous nitrogen or cooled solid (roll, pin, etc.)
Is used. The temperature of the cooled solid is preferably as low as possible within the range where condensation does not occur, and it is preferable to coat it with a non-adhesive material such as Teflon for the purpose of reducing friction with the dope. In particular, when making a thick wire having a thickness of 100 denier or more, it is preferable to use both airflow cooling and heat conduction cooling with a solid.

The coagulation liquid is preferably an organic solvent or water capable of washing out the solvent in the dope, but a liquid having a large molecular weight does not carry out the dope solvent into the fiber and the washing efficiency is poor. The concentration and temperature of the coagulating liquid affect the mechanical properties of the wire, but water at room temperature can also be used. However, when the solvent occupying most of the dope escapes from the filament, the orientation of the polybenzazole molecular chain is disturbed. As a means for recovering this, a method was invented in which a stretching of about 0.15% or more and about 3% or less was given in the solidification stage. The coagulation step here is a step in which the residual solvent amount in the filament is about 3.0% to about 30% with respect to the polybenzazole polymer, and 5% or more of the coagulation liquid penetrates into the filament. . That is, when stretching is started at the stage where only the surface of the filament is solidified, stress concentration occurs only in the surface layer where the solidification has progressed, and a difference between the inner and outer layers is generated, which is not preferable. It is considered that when the stretching is applied after the coagulation is advanced until the solvent almost disappears, the stretching effect is reduced because the orientation relaxation during the coagulation is partially irreversible. If the elongation at the solidification stage is less than about 0.15%, recovery from orientation disorder during solidification is insufficient. When stretched by about 3% or more, defects inside the filament grow large, and the strength of the wire decreases even when fracture does not occur in the manufacturing process. Further, the stretching may be performed once, or may be performed in multiple times. The stretch amount in this case is defined by the speed ratio before drying and at the start of solidification.

It takes a long time to sufficiently remove the solvent and the residual salt in the washing step. Therefore, in order to reduce the burden on the manufacturing equipment, it is possible to batch-wash the wire rod having a residual solvent amount of about 5% or less. However, it is preferable to reduce the residue in the filament as much as possible while controlling the process tension of the wire.

The washed fiber is dried by a known method. As a drying method, a method of passing through a heating furnace, using superheated steam, exposing to a reduced pressure, a method of using high frequency, or the like can be used. Drying is preferably performed at a temperature of 300 ° C. or lower in order to avoid damage to the fibers. In the present invention, these methods can be used together. The drying step may be performed without tension, but in order to obtain a higher elastic modulus, it is preferable to apply tension to dry under tension. Under a drying condition of about 300 ° C. or less, a tension of about 5 g / d can be applied. Even if the same tension is applied, the higher the temperature is, the higher the elastic modulus of the wire is. As a method of applying tension in the drying step, a method of winding on a spool made to spread with a spring and treating in an oven, a method of setting a strain rate in an online step, and the like can be used.

In the present invention, heat treatment can be carried out if necessary. For example, there is a well-known heat treatment method of polybenzazole which is passed through a well-known heating furnace under tension. Chen
The techniques found in the example of evy, US Patent 4,554,119 (November 19,1985) can be used together. The elastic modulus of the wire can be dramatically improved by the heat treatment.
The effect of heat treatment is not only this, but also has the advantage that the fiber structure becomes more dense and the equilibrium moisture content of the wire decreases. The tension required for the heat treatment is suitably 2 g / d to 10 g / d, which depends on the temperature and the deformation rate of the heat treatment furnace. A suitable stretching ratio in the heat treatment required to dramatically improve the elastic modulus is 0.6% to 8%, and more preferably 1.2% to 5% is stretched.

The average tensile strength of the wire obtained in the present invention is preferably at least about 10 g / d, more preferably about 15 g / d or more, and most preferably about 25 g / d or more. In order to increase the strength, it is necessary to optimize the solidification conditions, drying conditions and heat treatment conditions. The strongest contributor is the molecular weight of the polymer. A polymer having an intrinsic viscosity of 25 dl / g or more, a polymer having an intrinsic viscosity of 30 dl / g or more, and a polymer having a viscosity of 35 dl / g or more when higher strength is desired can be used. .

The polybenzazole wire is desired to have improved surface characteristics depending on the application. The polybenzazole wire is improved in adhesiveness, surface tension, and color tone by applying an ultraviolet absorber for increasing weather resistance and electron beam irradiation or other physical modification depending on the application. Alternatively, surface modification such as improvement of hardness and abrasion resistance by coating with ceramics and elasticity of the surface layer by coating with elastomer can be carried out.

The cross-sectional shape of the polybenzazole wire is preferably a perfect circle, an ellipse having an aspect ratio of 10 or less, or a rectangle. Further, the groove may have any shape such as a multi-sided groove and a polygon having 5 to 8 sides, but a shape that does not easily tear is preferable. Further, it is preferable that the manufactured wire has a substantially small curvature.

[0031]

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.
The intrinsic viscosity number of polybenzazole was determined for a methanesulfonic acid solution at 30 ° C.

Examples 1-5 and Comparative Example 1 A solution of polyphosphoric acid (diphosphorus pentoxide 8% by weight 84.3) in which 14.7% by weight of cis-polybenzoxazole having an intrinsic viscosity of 28 dl / g was dissolved was used. Mix and degas at 170 ° C in a shaft extruder. The dope was extruded at a temperature of 160 ° C. from a spinneret with a hole diameter of 1 to 10 holes shown in Table-1 and a length of 50 c.
m2O <0> C quench zone followed by 2 chill rolls of 21 cm diameter kept at 30 <0> C with cold water,
It passed through a 1 m coagulation tank and was led to a 7-roll roll having a diameter of 50 cm. The 7 rolls were driven so that the surface speed became higher in order, and a washing liquid was sprayed from a spray nozzle to the portion through which the filaments were passed for washing. The first roller speed from the inlet is 0.2% of the cooling roll speed (spinning speed)
Fast, the 7th roll is 1.
It was set to be 4% faster. The wire is shaken off in running water, washed for 2 to 7 days, dried in an oven at 120 ° C., and then wound up. Further, tension heat treatment was performed in an electric furnace at 590 ° C.

[0033]

[Table 1]

As shown in Table 1, the elastic modulus after heat treatment cannot reach 700 g / d, which is a requirement of the present invention, for an extremely thick wire.

Examples 6 and 7 and Comparative Example 2 A solution of polyphosphoric acid (diphosphorus pentoxide weight% 84.3) in which 14.7 weight% of cis-polybenzoxazole having an intrinsic viscosity of 26 dl / g was dissolved was used. Mix and degas at 170 ° C in a shaft extruder. The dope is extruded at 155 ° C. from a spinneret having 10 holes and a diameter of 0.6 mm. 50 cm2 in length
Following the 0 ° C. quench zone, it was passed through a pair of chill rolls kept at 30 ° C. with cold water rotating at a speed of 150 m / min, then passed through a 1 m coagulation tank, and led to 7 rolls with a diameter of 50 cm. The 7 rolls were driven so that the surface speed became higher in order, and a washing liquid was sprayed from a spray nozzle to the portion through which the filaments were passed for washing. First from the entrance
The second roller speed is 0.2% of the chill roll speed
Fast, the 7th roll is 1.
It was set to be 4% faster. The wire rod was shaken off in running water, washed for 2 days, dried in an oven at 120 ° C., and then wound (Example 6). Exactly the same as the experiment in which the dope filament was directly passed through the coagulation tank without passing through the cooling roll after passing through the quench (Example 7) and the dope filament was directly passed through the coagulation tank without using the quench (Comparative Example 2). An experiment was conducted through the steps of coagulation, washing with water and drying.
In the above three experiments, the filament temperature immediately before entering the coagulation tank was measured by IR THERMAL IMAGING R manufactured by Inframetrics.
It measured using ADIOMETER Model 760. The emissivity of the doped filament was 0.78.

[0036]

[Table 2]

As shown in Table 2, when the temperature of the dope filament entering the coagulation tank is higher than the solidification temperature of the dope, not only the elastic modulus but also the strength are significantly lowered. The solidification temperature of the dope is about 85 ° C.

Examples 8-10 and Comparative Example 3 A polyphosphoric acid (diphosphorus pentoxide weight% 84.3) solution containing 14.7 weight% of cis-polybenzoxazole having an intrinsic viscosity of 30 dl / g was dissolved in 2 parts. Mix and degas at 170 ° C in a shaft extruder. The dope is extruded at 175 ° C. from a spinneret having 10 holes and a diameter of 0.6 mm. 50 cm2 in length
Following the 0 ° C. quench zone, two 21 cm diameter chill rolls (speed 150 m /
Min), and then passed through a 1 m coagulation tank and led to 7 rolls having a diameter of 50 cm. The 7 rolls were driven so that the surface speed became higher in order, and a washing liquid was sprayed from a spray nozzle to the portion through which the filaments were passed for washing. The first roller speed from the inlet was set to 0.1% faster than the cooling roll speed. The speed of the individual rolls was set so that the seventh roll was faster than the chill roll speed, corresponding to the draw ratios shown in Table-3.
After the wire rod was shaken off in running water and washed for 2 days, 12
It was dried in an oven at 0 ° C. and then wound up.

[0039]

[Table 3]

When the draw ratio is 0.1% (the speed between the seven continuous rolls is constant), the elastic modulus of the wire is lowered.

[0041]

According to the present invention, it is possible to reduce the weight in applications where a high degree of dimensional stability is required, which has hitherto been possible to use only high strength steel and the like. In addition, it was possible to provide a reinforcing material which is lightweight and has excellent morphological stability even for tires and other composite materials.

[Brief description of drawings]

FIG. 1 is a schematic view of a manufacturing process in the present invention.

[Explanation of symbols]

1: Spinneret, 2: Dope filament, 3: Quench device, 4: Cooling roll, 5: Coagulation tank, 6: Washing roll,
7: Spray nozzle for washing, 8: Shaking device, 9:
It is a washing tank.

Claims (2)

[Claims] 1. A polybenzazole monofilament having a single yarn fineness of 15 dpf or more and an initial elastic modulus of 700 g / d or more. 2. A method for producing a polybenzazole monofilament having a single yarn denier of 15 dpf or more from a dope composed of an acid solvent and a polybenzazole polymer,
A method for producing a polybenzazole monofilament, which comprises the following steps. (1) A dope having a polymer concentration of 7 wt% or more is extruded from a die to form a dope filament, and (2) this dope filament is brought into contact with a non-solidifying fluid or a cooling solid to cool it to a temperature below the solidification temperature of the dope, and then ( 3) Remove most of the acid solvent while applying a draw of approximately 0.15% or more, and then dry. (4) Dry the washed fiment.