CA1289707C - Poly(arylene thioether-ketone) fibers and production process thereof - Google Patents

Abstract

ABSTRACT
Disclosed herein are poly(arylene thioether-ketone) fibers obtained by melt spinning a thermo-plastic material which comprises 100 parts by weight of a melt-stable poly(arylene thioether-ketone) (PTK) and optionally, up to 50 parts by weight of at least one of thermoplastic resins. The PTK has predominant recurring units of the formula

Description

~2~ 7 TITLE OF THE INVENTION:
POLYtARYLENE THIOETHER-KETONE) FIBERS
AND PRODUCTION PROCESS THEREOF

FIELD OF THE INVENTION
This invention relates to fibers obtained by melt-spinning a thermoplastic material composed principally of a melt-stable poly(arylene thioether-ketone) (hereinafter abbreviated as "PTK") having predominant recurring units of the formula ~ CO ~ S-~ , in which the -CO- and -S- are in the para position to each other, and more specifically to PTK fibers having high h~at resistance and strength, which are obtained by melt-spinning a thermoplastic material composed of the melt-stable PTK and optionally, at least one of other thermoplastic resins and/or one or more of various fillers.

BACKGROUND OF THE INVENTION
With the advance of weight-, thickness- and length-reducing technology in the field of the electronic and electric industry and with the recent advancement of weight-reducing technology in the fields of the automobile, aircraft and space industries, there has been a strong demand for crystalline thermoplastic - ~

~21~197~7 resins having heat resistance of about 300C or higher and permitting easy melt processing in recent years.
As crystalline, heat-resistant, thermoplastic resins developed to date, there are, for example, poly(butylene terephthalate), polyacetal, poly(p-phenylene thioether), etc. These resins are however unable to meet the recent requirement level for heat resistance.
Polyether ether ketones (hereinafter abbreviated as "PEEKs") and polyether ketones (hereinafter abbreviated as "PEKs") have recently been developed as heat-resistant resins having a melting point of about 300C or higher. These resins are crystalline thermoplastic resins. It has therefore been known that conventional melt processing techniques such as extrusion, injection molding, melt spinning, blow molding and laminate molding can be applied to easily ~orm them into various molded or formed articles such as extruded products, injection-molded products, fibers and films. These reslns however use expensive fluorine substituted aromatic compounds such as 4,4'-difluorobenzophenone as their raw materials.
Limitations are thus said to exist to the reduction of their costs. It is also pointed out that these resins involve a problem in expanding their consumption.

~9~(37 Based on an assumption that PTKs could be promising candidates for heat-resistant thermoplastic resins like PEEXs and PEKs owing to their similarity in chemical structure, PTKs have been studied to some extent to date. There are some disclosure on PTKs, for example, in Japanese Patent Laid-Open No. 58435/1985 thereinafter abbreviated as "Publication A"), German Offenlegungsschrift 34 05 523Al (hereinafter abbreviat-ed as "Publication B"), Japanese Patent Laid-Open No.
10 104126/1985 (hereinafter abbreviated as "Publication C"), Japanese Patent Laid-Open No. 13347/1972 (hereinafter abbreviated as "Publication ~"), Indian J.
Chem., 21A, 501-502 (May, 1982) (hereinafter abbreviated as "Publication E"), and Japanese Patent 15 Laid-Open No. 221229/1986 (hereinafter abbreviated as "Publication F").
Regarding the PTKs described in the above publications, neither molding nor forming has however succeeded to date in accordance with conventional melt processing techniques. Incidentally, the term "conventional melt processing techniques" as used herein means usual melt processing techniques for thermoplastic resins, such as extrusion, injection molding, melt spinning, blow molding, laminate molding, etc.

1289~

The unsuccessful molding or forming of PTKs by conventional melt processing techniques is believed to be attributed to the poor melt stability of the prior : art PTKs, which tended to lose their crystallinity or to undergo crosslinking and/or carbonization, resulting in a rapid increase in melt viscosity, upon their melt processing.
It was at-temp-ted to produce some molded or formed products in Publications A and B. Since the PTKs had poor melt stability, certain specified types of molded or formed products were only obtained by a special molding or forming process, where PTKs were used only as a sort of binder, being impregnated into a great deal of reinforcing fibers of main structural materials and molded or formed under pressure.
Since the conventional PTKs are all insufficient in melt stability as described above, it has been unable to obtain formed products such as fibers even from compositions of the PTKs with another thermo-plastic resin and a filler, to say nothing of the PTKsalone, by applying conventional melt processing techniques~

OBJECTS AND SUMMARY OF THE INVENTION
An object of this invention is to overcome the above-mentioned drawbacks of the prior art and hence to '128~

provide fibers by melt-spinning a melt-stable PTK which permits easy application of a conventional melt processing technique.
Another object of this invention is to provide fibers, which have high heat resistance and strength, by melt-spinning a thermoplastic material which comprises a melt-stable PTK alone or a composition of a melt-stable PTK and at least one of thermoplastic resins.
A further object of this invention is to produce PTK fibers economically.
The present inventors started an investigation with a view toward using economical dichlorobenzo-phenone and/or dibromobenzophenone as a raw material for PTRs without employing any expensive fluorine-substituted aromatic compound. In addition, a polymerization process was designed in an attempt to conduct polymerization by increasing the water content in the polymerization system to an extremely high level compared to processes reported previously, adding a polymerization aid and suitably controlling the profile of the polymerization temperatuxe. As a result, high molecular-weight PTKs were obtained economically. The PTXs obtained by the above process were however still dissatisfactory in melt stability.

~897~7 Thus, the present inventors made further improvements in the polymeri~ation process. It was then revealed that melt-stable PTKs, which permitted the application of conventional melt processing techniques, could be obtained by conducting polymerization without addition of any polymerization aid while paying attention to the selection of a charge ratio of monomers, the shortening of the polymerization time at high temperatures, the selection of a material for a polymerization reactor, etc. and if necessary, by conducting a stabilization treatment in a final stage of the polymerization. It was also found that PTR
fibers having high heat resistance and strength could be obtained easily from a thermoplastic material composed principally of the melt-stable PTKs by general melt-processing techniques.
These findings have led to the completion of the present invention.
In one aspect of this invention, there is thus provided poly(arylene thioether-ketone~ fibers oDtained by melt-spinning a thermoplastic material which comprises:
~ A) 100 parts by weight of a melt-stable poly(arylene thioether-ketone) having predominant recurring units of the formula ~ CO ~ S-~ , wherein the -CO- and -S- are in the para position to 7CI~

each other, and having the following physical properties ta) - (c):
ta) melting point, Tm being 310-380C;
(b) residual melt crystallization enthalpy, ~Hmc (420C/10 min) being at least 10 J/g, and melt crystallization temperature, Tmc (420C/10 min) being at least 210C, wherein QHmc (420C/10 min) and Tmc (420C/10 min) are determined by a differential scanning calorimeter (hereinafter abbreviated as "DSC") at a cooling rate of 10C/min, after the poly(arylene thioether-ketone) is held at 50C for 5 minutes in an inert gas atmosphere, heated to 420C at a rate of 75C/min and then held for 10 minutes at 420C; and (c) reduced viscosity being 0.3-2 d~/g as determined by viscosity measurement at 25C and a polymer concen~ration of 0.5 g~d2 in 98 percent by weight sul~uric acid; and optionally, ~B) up to 50 parts by weight of at least one of thermoplastic resins.
In another aspect of this invention, there is also provided a process for the production of poly(arylene thioether-ketone) fibers, which comprises melt-extruding the above-described thermoplastic material at an extrusion temperature of 320-430C
through a spinneret, stretching the resultant fibers to 8~3~70~

a draw ratio of from 1.2:1 to 8:1 within a temperature range of 120-200C, and then heat setting the thus-stretched fibers at 130 370C for 0.1-1,000 seconds.
Owing to the use of the PTK having melt stability, the present invention has made it possible for the first time to obtain PTK fibers having high heat resistance and strength from the PTK or a thermoplastic resin composition composed principally of the PTK in accordance with a melt-spinning technique.

DETAILED DESCRIPTION OF THE INVENTION
Features of the present invention will hereinafter be described in detail.
Chemical Structure of PTKs The melt stable PTKs according to the present invention are poly(arylene thioether-ketones) ~PTRs) having predominant recurring units of the formula ~ CO ~ S-~ wherein the -CO- and -S- are in the para position to each other. In order to be heat-resistant polymers comparable with PEEXs and PE~s, the PTKs of this invention may preferably contain, as a main constituent, the above recurring units in a proportion greater than 50 wt.%, more preferably, of 60 wt.~ or higher, most preferably, of 70 wt.% or higher.
If the proportion of the recurring units is 50 wt.~ or less, there is a potential problem that the crystal-~2~

linity of the polymer is reduced and its heat resis-tance is reduced correspondingly.
Exemplary recurring units other than the above recurring units may include:
S ~ CO ~ S-~ (except for the recurring unit in which the -CO- and -S- are in the para position to each other.);
~CO~S~;
~o~o~S~;
~ CH~ ~ S-~ ;
~S~;
~S~;
~S~;
~- ~ S2 ~ S-~ ; and ~ S-t (wherein R means an alkyl group Rm having 5 or less carbon atoms and m stands for an integer of 0-4.).
It is desirable that the melt stable PTKs of this invention are uncured polymers, especially, uncured linear polymers. The term "cure" as used herein means a molecular-weight increasing treatment for a polymer by a method other than a usual polycondensation reaction, for example, by a crosslink-ing, branching or molecular-chain extending reaction, particularly, a molecular-weight increasing treatment by a high-temperature heat treatment or the like. In ,.

~8g707 general, "curing" causes a PTX to lose or decrease its melt stability and crystallinity. Curing therefore makes it difficult to employ conventional melt processing of a PTX~ Even if fibers are obtained, they tend to have a low density and reduced crystallinity, in other words, may not be regarded as "heat-resistant fibers" substantially. Curing is hence not preferred.
However, PTKs having a partially crosslinked and/or branched structure to such an extent still allowing the application of conventional melt processing techniques are still embraced in the present invention. For example, PTKs obtained by conducting polymerization in the presence of a small amount of a crosslinkiny agent (e.g., polychlorobenzophenone, polybromobenzophenone or the like) and PTKs subjected to mild curing can be regarded as melt-stable PTKs useful for fibers according to this invention.
Physical Properties of PTKs The melt stable PTKs useful in the practice of this invention have the following physical properties.
(a) As indices of the characteristics of heat-resistant polymers, their melting points, Tm range from 310 to 380~C.
(b) As indices of the melt stability of polymers to which conventional melt processing techniques can be applied, their residual melt crystallization enthalpies, QHmc (420C/10 min) are at least 10 J/g, and their melt crystallization temperatures, Tmc ~420C/10 min) are at least 210C.
(c) In the case of extrusion products such as fibers, their shaping is difficult due to drawdown or the like upon melt forming unless the molecular weight is sufficiently high. They should have a sufficiently high molecular weight~ As indices of the molecular weights of the polymers, their reduced viscosities ~red should be within the range of 0.3-2 d/g.
In the present invention, each reduced viscosity nred is expressed by a value as measured at 25C
and a polymer concentration of 0.5 g/d~ in 98 percent by weight sulfuric acid as a solvent.
lS (d) As indices of the characteristics of highly-crystalline polymers, the polymers have a density of at least 1.34 g/cm3 at 25C when annealed at 280C for 30 minutes.
Next, the physical properties o the melt stable PTKs useful in the practice of this invention will be described in detail.
(1) Heat resistance:
The melting point, Tm of a polymer serves as an index of the heat resistance of the polymer.
The PTKs useful in the practice of this invention have a melting point, Tm of 310-380C, ~L.;28970~

preferably 320-375C, more preerably 330~370C.
Those having a melting point, Tm lower than 310C are insufficient in heat resistance as heat-resistant resins comparable with PEEKs and PEKs. On the other hand, it is difficult to perform the melt processing of those having a melting point, Tm higher than 380C
without decomposition. Such an excessively low or high melting point is undesired.

(2) Melt stability:
The greatest feature of the PTRs useful in the practice of this invention resides in that they have melt stability sufficient to permit the application of conventional melt processing techniques.
All the conventional PTKs have low melt stability and tend to lose their crystallinity or to undergo crosslinking or carbonization, resulting in a rapid increase in melt viscosity, upon their melt processing.
It is hence possible to obtain an index of the melt processability of a PTR by investigating the residual crystallinity of the PT~ after holding it at an elevated temperature of its melt processing temperature or higher for a predetermined period of time. The residual crystallinity can be evaluated quantitatively in terms of meLt crystallization enthalpy. Specifically, the residual melt crystalliza-12~g7~7 tion enthalpy, QHmc (420C/10 min) and its meltcrystalliæation temperature, Tmc (420C/10 min~ of the PTK which are determined by a DSC at a cooling rate of 10C after the PTK is held at 50C for 5 minutes in an inert gas atmosphere, heated to 420C at a rate of . 75C/min and then held for 10 minutes at 420C, can be used as measures of its melt stability. In the case of a PTK having poor melt stability, it undergoes crosslinking or the like at the above high temperature condition of 420C and loses its crystallinity substantially.
The melt stable PTKs useful in the practice of this invention are polymers whose residual melt crystallization enthalpies, QHmc (420C/10 min) are preferably at least 10 J/g, more preferably at least 15 J/g, most preEerably at least 20 J/g and whose melt : crystallization temperatures, Tmc (420C/10 min~ are preferably at least 210C, more preferably at least 220C, most preferably at least 230C.
A PTK, whose ~Hmc (420C/10 min) is smaller than 10 ~/g or whose Tmc (420C/10 min) is lower than 210C, tends to lose its crystallinity or to induce a melt viscosity increase upon its melt processing, so that dificulties are encountered upon application of conventional melt processing techniques such as melt spinning.

~289707 (3) Molecular weight:
The solution viscosity, or example, reduced viscosity nred of a polymer can be used as an index of its molecular weight.
When a PTX or a PTK composition is subjected to melt spinning, drawdown or the like may occur as a problem upon its melt processing.
Therefore, the molecular weight which is correlated directly to the melt viscosity of the PTK is also an important factor for its melt processability.
In order to apply conventional melt processing techniques, high molecular-weight prKs whose reduced viscosities, nred are preferably 0.3-2 d~/g, more preferably 0.5-2 dQ/g, are desired. Since a PTK whose nred is lower than 0.3 d~/g has a low melt viscosity and high tendency of drawdown, it is difficult to apply conventional melt processing techniques such as melt spinning. Further, fibers from such a PTK are insufficient in mechanical properties.
On the other hand, a PTK whose nred exceeds 2 d~/g is very difficult in production and process.

(4) Crystallinity:
As an index of the crystallinity of a polymer, its density is used.
The PTKs useful in the practice of this invention are desirably polymers whose densities (at :~LZIS 9~7 25C) are preferably at least 1.34 g/cm3, more preferably at least 1.35 g/cm3 when measured in a crystallized form by annealing them at 280C for 30 minutes. Those having a density lower than 1.34 g/cm3 have potential problems that they may have low crystallinity and hence insufficient heat resistance and mechanical properties of resulting fibers may also be insufficient.
In particular, PTKs crosslinked to a high degree (e.g., the PTKs described in Publication A) have been reduced in crystallinity and their densities are generally far lower than 1.34 g/cm3.
Production Process of PTKs The melt stable PTKs useful in the practice of this invention can each be produced, for example, by subjecting an alkali metal sulfide and a dihalogenated aromatic compound, preferably, dichlorobenzophenone and/or dibromobenzophenone to dehalogenation and sulfuration, for a short period of time, in the substantial absence of a polymerization aid (a salt of a carboxylic acid, or the like), in an aprotic polar organic solvent, preferably, an organic amide solvent (including a carbamic amide or the like) and in a system having a water content far higher compared with conventionally-reported polymeri~ation processes while controlling the temperature profile suitably, and if ~2l~ )7 necessary, by choosing the material of a reactor suitably.
Namely, the melt stable PTKs useful in the practice of this invention can each be produced suitably by polymerizing an alkali metal sulfide and a dihalogenated aromatic compound consisting principal-ly of 4,4'-dichlorobenzophenone and/or 4,4'-dibromo-benzophenone by dehalogenation and sulfuration under the following conditions (a)-(c) in an organic amide solvent.
(a) ratio of the water content to the amount of the charged organic amide: 2.5-15 (mole/kg);
(b) ratio of the amount of the charged dihalogenated aromatic compound to the amount of the charged alkali metal sulfide: 0.95-1.2 (mole/mole); and (c) reaction temperature: 60-300C with a proviso that the reaction time at 210C and higher is within 10 hours.
The melt stable PTKs can be obtained more suitably when a reactor at least a portion of which, said portion being brought into contact with the reaction mixture, is made of a corrosion-resistant material such as titanium material.
Optionally, at least one halogen-substituted aromatic compound having at least one substituent group having electron-withdrawing property at least equal to .;

9~7~7 -CO- group (preferably, ~,4'-dichlorobenzophenone and/or 4,4'-dibromobenzophenone employed as a monomer) may be added and reacted (as a stabilization treatment in a final stage of the polymerization) so as to obtain PTKs improved still further in melt stability.
The melt stable PTKs employed in the present invention ~ay preferably be uncured polymers as described above. They may however be PTKs in which a crosslinked structure and/or a branched structure has been incorporated to a certain minor extent. In order to obtain a PTK with a branched or crosslinked struc-ture introduced therein, it is preferable to have a polyhalogenated compound, especially, a polyhalogenated benzophenone having at least three halogen atoms exist as a crosslinking agent in the polymerization reaction system in such an amount that the charge ratio of the monomeric dihalogenated aromatic compound to the polyhalogenated benzophenone ranges from 100/0 to 9S/5 (mole/mole). If the amount of the charged ~o polyhalogenated benzophenone is too much, physical properties of the resulting PTK, such as their melt processability, density and crystallinity, will be reduced. It is hence not preferable to charge such a polyhalogenated benzophenone too much.
Thermoplastic Resin , 1;2~39~(~7 The thermoplastic material used as a raw material for the melt-spinning in this invention may be composed of the melt-stable PTK alone. In view of processability, physical properties, economy and the like, it may also be a resin composition obtained by mixing at least one of other thermoplastic resins in a proportion of 0-50 parts by weight, preferably 0-40 parts by weight, and more preferably 0-30 parts by weight, all, per 100 parts by weight of the PTX. It is not preferable to add the thermoplastic resin in any amount greater than 50 parts by weight, because such a high proportion results in fibers of reduced heat resistance and heat shrinkage resistance.
As exemplary thermoplastic resins useful in the present invention, may be mentioned resins such as poly~arylene thioethers), PEEKs and PEKs, polyamides (including Aramids), polyamideimides, polyesters (including aromatic polyesters and liquid crystalline polyesters), polysulfones, polyether sulfones, polyether imides, polyarylenes, poly(phenylene ethers), polycarbonates, polyester carbonates, polyacetals, fluoropolymers, polyolefins, polystyxenes, polymethyl methacrylate, and ABS; as well as elastomers such as fluororubbers, silicone rubbers, olefin rubbers, acrylic rubbers, polyisobutylenes (including butyl 7~7 rubber), hydrogenated SBR, polyamide elastomers and polyester elastomers.
Among the above-exemplified thermoplastic resins, poly(arylene thioethers)l especially, poly(arylene thioethers) having predominant recurring units of the formula ~ S-~ ~hereinafter abbre-viated as "PATEs"; said recurring units accounting for at least 50 wt.%) are preferred, because the PATEs have good compatibility with the PTK and their blending with the PTK can provide fibers which have mechanical properties improved over those obtained from the PTK
alone at room temperature and also heat resistance improved over -those obtained from the PATEs alone and are well balanced in heat resistance and mechanical properties.
Other components:
In this invention, one or more of fibrous fillers and/or inorganic fillers may be added in a proportion up to 10 parts by weight per 100 parts by weight of the PTK as desired. If the proportion of the filler exceeds 10 parts by weight, there is a potential problem that the processability may be deteriorated to a considerable extent and the physical properties of the resulting fibers would be deteriorated.
As exemplary fibrous fillers usable in thls invention, may be mentioned fibers such as glass ~289'7~7 fibers, carbon fibers, graphite fibers, silica fibers, alumina fibers, zirconia fibers, silicon carbide fibers and Aramid fibers; as well as whiskers such as potassium titanate whiskers, calcium silicate 5 (including wollastonite) whiskers, calcium sulfate whiskers, carbon whiskers, silicon nitride whiskers and boron whiskers.
As exemplary inorganic fillers~ may be mentioned talc, mica, kaolin, clay, silica, alumina, silica-alumina, titanium oxide, iron oxides, chromium oxide,calcium carbonate, calcium silicate, calcium phosphate, calcium sulfate, magnesium carbonate, magnesium phosphate, silicon, carbon (including carbon black), graphite, silicon nitride, molybdenum disulfide, glass, hydrotalcite, ferrite, samarium-cobalt, neodium-iron-boron, etc., all, in a powder form.
These fibrous fillers and inorganic fillers may be used either singly or in combination.
In this invention, it is feasible to add one or more of additives such as stabilizers, anticorrosives, lubricants, surface-roughening agents, ultraviolet absorbents, nucleating agents, mold-releasing agents, colorants, coupling agents and antistatic agents, as needed.
Production Process of Fibers . .

~L2~39~

The PTK fibers of this invention can be produced by charging a thermoplastic material, which is composed of the melt stable PTK or the composition of the melt-stable PTK and at least one of thermoplastic resins, for example, into a spinneret-equipped extruder in the air or preferably, in an inert gas atmosphere, extruding the thermoplastic material at an extrusion temperature of 320-~30C, stretching the resultant fibers to a draw ratio of from 1.2:1 to 8:1 within a ` 10 temperature range of 120-~00C, and then heat setting the thus-stretched fibers at 130-370C for 0.1-1,000 seconds. Upon extrusion through the spinneret, fibers are generally taken up at a draw down ratio (the ratio of the take-up speed of spun fibers to the discharge rate of the resin from the spinneret) of from 1:1 to 1000:1, preferably, from 5:1 to 500:1.
If the extrusion temperaturè from the spinneret is lower than the above temperature range, it is difficult to achieve smooth spinning. If it is too high on the contrary, deterioration of the resin is ; induced. Extrusion temperatures outside the above ranga are hence not preferred. The fibers extruded from the spinneret are stretched in the solid state and are hence oriented. The stretching is carried out at a temperature not higher than the melting point of the PTK, preferably, at 120-200C. The stretching step ~IL2897~7 may be performed, for example, by stretching melt-spun and unstretched fibers in a dry heat bath or wet heat bath of a high temperature or on a hot plate of a high temperature. If the stretching temperature is outside the specified temperature range, end breakages, fuzzing and/or melt bonding tends to take place. Stretching temperatures outside the above temperature range are hence not preferred~
The draw ratio ranges from 1.2:1 to 8:1. Draw ratios smaller than 1.2:1 are difficult to obtain high-strength fibers. On the other hand, draw ratios greater than 8:1 encounter difficulties in stretching and induce end breakages and/or fuzzing. Draw ratios outside the above range are therefore not preferred.
By applying heat setting subsequent to stretching, fibers having high strength and a small heat shrinkage factor can be obtained.
Physical Properties of Fibers The PTK fibers of this invention generally have a fiber diameter of 0.5-1,000 ~m, preferably, 1-300 ~m and has the following excellent physical properties.
ta) density o~ PTR portions being at least 1.34 g/cm3 at 25C;
(b) tensile strength being at least 10 kg/mm2 at 23C or at lea~t 3 kg/mm2 at 250C;
(c) tensile modulus being at least 100 kg/mm2 ~289~

at 23C or at least 30 kg/mm2 at 250C;
(d) tensile elongation being at least 5~ at 23C; and (e) heat shrinkage (220C/30 min) being at most 20%.
(Measurements of physical properties) * Density of PTK portions (25C):
Where the thermoplastic material as the raw material of the fibers is composed of the PTK alone, the density (25C) of PTK portions is the same as the density (25C) of the fibers. Where the thermoplastic material contains the thermoplastic resin and/or filler as a further component in addition to the PTK, a sample is separately prepared under the same conditions for the production of the fibers by using the same thermoplastic material except for the omission of the PTK, and the density (25C) of PTK portions can be determined from the density (25C) of the fibers and the density (25C) of the sample free of the PTK.

Density of the fibers =
Weiaht fraction of PTK Portions 1/{ Density of PTX portions + 1 - (Weight fraction of PTX portions }
Density of sample free of PTK
* Tensile strength:
JIS-L1013 was followed (sample length: 300 mm;
drawing rate: 300 mm/min).
* Tensile modulus:

~2t39t7~7 JIS-L1013 was followed ~stress (modullls of elasticity) at 1% deformation (elongation)].
* Tensile elongation:
JIS-L1013 was followed.
* Heat shrinkage (220C/30 min):
After aging each fiber sample at 220C for 30 minutes, the degree of shrinkage of the sample was determined.
As has been described above, the PTK fibers of this invention are fibers obtained by using a melt-stable PTK having a high molecular weight of 0.3-2 dl/g in terms of reduced viscosity, a density of 1.34 g/cm3 when annealed at 280C for 30 minutes and a melting point, Tm of 310-380C. The PTK fibers thus have high heat resistance and strength.
A lication Fields of PTK Fibers of This Invention Pp Although the fibers-of this invention are not used in any particularly limited fields, industrial filters, heat-insulating materials, reinforcing fibers, insulating tapes, insulating cloths, fireproof wears, high-temperature gloves, prepreg fibers, tension members for optical-fiber cables, etc. may be mentioned by way of example as their specific application fields.

ADVANTAGES OF THE INVENTION

~89707 PTK fibers having high heat resistance and strength were successfully obtained by the present invention. PTKs according to conventional techniques had poor melt stability, so that melt spinning was not applicable thereto. Owing to the use of the novel melt-stable PTK in this invention, melt spinning has become feasible and moreover, PTK fibers having excellent physical properties have been provided.
The PTK fibers according to this invention can be used in a wide variety of fields in which heat resistance and strength are required.

EMBODIME~TS OF T~E INVENTION
. _ . _ ....
The present invention will hereinafter be described more specifically by the following Examples, Comparative Examples and Experiments. It should however be borne in mind that the scope of the present invention is not limited to the following Examples and Experiments.
Experiments Synthesis Experiment 1: (Synthesis of Melt-Stable PTR) A titanium-lined reactor was charged with 90 moles of 4,4'-dichlorobenzophenone (hereinafter abbreviated as "DCBP"; product of Ihara Chemical Industry Co., Ltd.), 90 moles of hydrated sodium sulfide (water content: 53.6 wt.~; product of Sankyo ~289707 Xasei Co., Ltd.) and 90 kg of N-methylpyrrolidone (hereinafter abbreviated as "NMP") (water content/NMP =
5.0 moles/kg). After the reactor being purged with nitrogen gas, the resultant mixture was heated from room temperature to 240C over 1.5 hours and then maintained at 240C for 2.5 hours. In order to apply the stabilization treatment in the final stage of the polymerization, the reaction mixture was heated up to 260C over 1 hour while charging under pressure a mixture composed of 9.0 moles of DCBP, 15 kg of NMP and 75 moles of water. The resultant mixture was maintained further at 260C for 0.3 hour to react them.
The reactor was cooled, and the reaction mixture in the form of a slurry was taken out of the reactor and was then poured in~o about 200 ~ of acetone. The resultant pol~ner was precipitated, recovered by filtration, and then washed twice with acetone and additionally twice with water. Acetone and water were removed to obtain the polymer in a wet form. The wet polymer was dried at 80C for 12 hours under reduced pressure, thereby obtaining Polymer Pl.
When the physical properties of Pol~ner Pl were measured, Tm was found to be 366C, ~Hmc (420C/10 min) 25 56 J/~, ~nc (420C/10 min) 306C, and the reduced viscosity 0.81 d~/g. In addition, the density (25C) ~3970~

~ 27 -of Polymer Pl was 1.30 g/cm3 in an amorphous foxm and 1.35 g/cm3 in an annealed form.
<Measurement Methods of Physical Properties>
Measurement of melting point:
With respect to the PTK thus obtained, the melting point, Tm was measured as an index of its heat resistance. The measurement was performed in the following manner. About 10 mg of each PTK (powder) ~as weighed. The sample was held at 50C for 5 minutes in an inert gas atmosphere and then heated up at a rate of 10C/min so as to measure its mel-ting point on a DSC
(Model TClOA; manufactured by Mettler Company).
Measurement of residual melt crystallization enthalpy:
With respect to the PTK obtained above, the residual melt crystallization enthalpy, ~Hmc (420C/10 min) was measured as an index of its melt stability. Namely, the temperature corresponding to a peak of melt crystallization measured by the DSC is represented by Tmc ~420C/10 min) and the amount of heat converted from the area of the peak was taken as residual melt crystallization enthalpy, ~Hmc (420C/10 min). Described specifically, about 10 mg of the PTK (powder form) was weighed. After holding the PTK at 50C for 5 minutes in an inert gas atmosphere, it was heated up at a rate of 75C/min to 420C and held at that temperature for 10 minutes.

3L;~8~707 While cooling down the PTK at a rate of lO~C/min, its ~Hmc (420C/10 min) and Tmc (420C/10 min) were measured.
Measurements of density and solution vi_cosity:
The density of the PTK was measured as an index of its crystallinity of the PTK. Namely, the PTK
(powder) was first of all placed between two polyimide films ("Kapton", trade mark; product of E.I. du Pont de Nemours & Co., Inc.). Using a hot press, it was preheated at 385C for 2 minutes and then press-formed at 385C for O.S minute. It was then quenched to obtain an amorphous sheet whose thickness was about 0.15 mm. A part of the amorphous sheet was used directly as a sample, while the remaining part was 15 annealed at 280C for 30 minutes to use it as an annealed sample with an increased degree of crystal-linity. Their densities were measured separately at 25~C by means of a density gradient tube (lithium bromide/water).
The solution viscosity (reduced viscosity, nred) of the PTK was also measured as an index of its molecular weight.
Namely, the PTK was dissolved in 98 wt.%
sulfuric acid to give a polymer concentration of 0.5 g/dl. The viscosity of the resultant solution was ~2~g~7 then measured at 25C by means of a Ubbellohde viscometer.
Example_l (Melt Spinning) Under a nitrogen gas stream, the PTK polymer, Pl was charged into an extruder having a cylinder diameter of 35 mm and equipped with a spinneret which had 40 fine holes, each of 0.5 mm across. The PTR polymer was extruded at an extrusion temperature of 375C and a draw down ratio ~the ratio of the take-up speed of spun fibers to the discharge rate of the resin from the spinneret) of about 200, and then was cooled through a nitrogen gas environment, so that unstretched fibers were obtained.
The unstretched fibers were stretched 3.2 times on a hot plate of i60C and then caused to pass for 2.5 seconds through hot air of 280C so as to heat set them.
The thus-obtained fibers had the followinq physical properties. Fiber diameter: 20 ~m. Tensile strength (23C): 38 Kg/mm2. Tensile modulus (23C):
400 kg/mm2. Tensile elongation (23C): 25%. Heat shrinkage (220C/30 min): 7.5~. Density (25C): 1.36 g/cm3.
The tensile strength of the fibers was measured after they were left over for 500 hours in an atmos-phexe of 220C. It was 35.5 kg/mm2.

~28g7~7 At 250C, their tensile strength was 20.5 kg/mm2 while their tensile modulus was 150 kg/mm2.
Example 2:
Polymer P2 was obtained by conducting polymeri-zation in the same manner as in Synthesis Experiment 1except that 90.9 moles of DCBP was charged instead of 90 moles of DCBP and the reaction time at 240C was changed to 1.5 hours.
Example 3:
Polymer P3 was obtained by conducting polymeri-zation in the same manner as in Synthesis Experiment 1 except that a mixture of 89.1 moles of DCBP and 0.9 mole of 2,2',4,4'-tetrachlorobenzophenone was charged instead of 90 moles of DCBP.
ComParative Example 1:
Polymer CPl was obtained by conducting polymeri-zation in the same manner as in Synthesis Experiment 1 except that 91.8 moles of DCBP were charged instead of 90 moles of DCBP and that the reaction time at 240C
was changed to 2 hours.
Comparative Example 2-.

Polymer CP2 was obtained by conducting polymeri-zation in the same manner as in Synthesis Experiment 1 except that a mixture of 85 moles of DCBP and 5.0 moles Of 2,2l,4,4'-tetrachlorobenzophenone was charged instead of 90 moles of DCBP.

~2~397~7 The individual PTKs were separately melt-spun in the same manner as in Example 1, thereby producing unstretched fibers respectively.
Physical properties of the PTKs and their processability upon melt spinning are shown in Table 1.
Those unstretched fibers were separately stretched 3.2 times on a hot plate of 160C and then heat set at 1.02 times in hat air of 280C.
Physical properties of stretched yarns of Examples 2-3 are summarized in Table 2.

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Example 4:
Using the facilities similar to those employed in Example 1, unstretched fibers which had been extruded at 370C and spun at a draw down ratio of about 100 were stretched 5.0 times in an atmosphere of 156C, heat set in hot air of 315C.
The thus-obtained fibers had the following physical properties. ~Fiber diameter: 23 ~m. Tensile strength (23C): 41 Kg/mm2. Tensile modulus (23~C):
430 kg/mm . Heat shrinkage (220C/30 min): 6.2%.
Density (25C): 1.36 g/cm3.
The tensile strength of the fibers was measured after they were left over for 500 hours in an atmos-phere of 220C. It was 37 kg/mm2.
At 250C, their tensile strength was 25 kg/mm while their tensile modulus was 160 kg/mm2.
Example 5:
Under a nitrogen gas stream, the PTX polymer, Pl was charged into an extruder having a cylinder diameter of 40 mm and equipped with a spinneret which had 6 fine holes, each of diameter 1~0 mm. The PTK polymer was extruded at an extrusion temperature of 370C and a draw down ratio of 10 and then cooled in warm water of 50C, so that unstretched fibers were obtained.

97~7 The unstretched fibers were stretched 3.3 times in hot glycerin of 155C, and heat set with 4%
relaxation in the hot air of 300C.
The thus-obtained fibers had the following 5 physical properties. Fiber diameter: 170 ~m. Tensile strength (23C): 41 Kg/mm . Tensile modulus (23C):
380 kg/mm . Heat shrinkage (220C/30 min): 6.5~.
Density (25C): 1.36 g/cm .
The tensile strength of the fibers was measured after they were left over for 300 hours in an atmos-phere of 220C. It was 38.5 kg/mm .
At 250C, their tensile strength was 17 kg/mm2 while their tensile modulus was 130 kg/mm2.
Synthesis Experiment 2: (Synthesis of poly para-phenylene sulfide) A 20 ~ autoclave was charged with 11.0 kg ofNMP and 4.24 kg of hydrated sodium sulfide (water content: 53.98 wt.%: product of Nagao Soda K.K.) (25.0 moles as sodium sulfide). The resultant mixture was heated up gradually to 203C under stirring over about 2 hours in a nitrogen gas atmosphere, so that 1.59 kg of water, 1.96 kg of NMP and 0.58 mole of hydrogen sulfide were distilled out.
After cooling down the reaction mixture to 25 130C, 3.59 kg (24.42 moles) of p-dichlorobenzene 3L~897 017 (p-DCB) and 3.17 kg of NMP were added. The resultant mixture was heated at 215C for 8 hours for polymeri-zation. Thereafter, 1.275 kg of water was added and in a nitrogen atmosphere, the resultant mixture was heated up to 265C. At that temperature, polymerization was conducted for 4 hours. After cooling the reaction mixture, the resultant polymer was collected ~rom the reaction mixture by filtration, washed repeatedly with deionized water, and then dried at 100C under reduced pressure.
The thus-obtained polymer was a crystalline polymer having a melt viscosity was 3,000 poises (310C, shear rate: 1,200/sec) and a melting point, Tm of 282C. The polymer (hereinafter abbreviated as "PPS") was melt-extruded at 330C, thereby obtaining pellets.
Examples 6-10 & Comparative Examples 3-6:
Polymer Pl obtained above in Synthesis Experiment 1 was used as a PTK. The PTK was added with PPS obtained above in Synthesis Experiment 2, thereby obtaining a raw material for spinning.
To 100 parts by weight of Polymer Pl (PTK), the PPS obtained in Synthesis Experiment 2 were added at the proportions given in Table 3. The resultant 25 mixtures were separately extruded at 370-380C into pellets.

:~2~3~7~:)7 Using those pellet samples separately as raw materials, melt spinning was performed by the same facilities as those used in Example 1, thereby obtaining unstretched fibers.
The thus-obtained fiber samples were separately stretched 3.0 times on a hot plate and then heat set at 275C while maintaining their length constant.
Temperature conditions for the hot plate are also given in Table 3. All the the resultant fiber samples had a fiber diameter of 20 ~m.
: Physical properties of the thus-obtained fiber samples are also shown in Table 3.

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In contrast, it is appreciated that the Examples of the present invention, in each of which the proportion of the PPS was not greater than 50 parts by weight, gave fibers excellent in tensile strength and heat shrinkage and featuring well-balanced heat resistance and strength.

Claims (14)

1. Poly(arylene thioether-ketone) fibers obtained by melt-spinning a thermoplastic material which comprises:
(A) 100 parts by weight of a melt-stable poly(arylene thioether-ketone) having predominant recurring units of the formula , wherein the -CO- and -S- are in the para position to each other, and having the following physical properties (a) - (c):
(a) melting point, Tm being 310-380°C;
(b) residual melt crystallization enthalpy, .DELTA.Hmc (420°C/10 min) being at least 10 J/g, and melt crystallization temperature, Tmc (420°C/10 min) being at least 210°C, wherein .DELTA.Hmc (420°C/10 min) and Tmc (420°C/10 min) are determined by a differential scanning calorimeter at a cooling rate of 10°C/min, after the poly(arylene thioether-ketone) is held at 50°C for 5 minutes in an inert gas atmosphere, heated to 420°C at a rate of 75°C/min and then held for 10 minutes at 420°C; and (c) reduced viscosity being 0.3-2 dl/g as determined by viscosity measurement at 25°C and a polymer concentration of 0.5 g/dl in 98 percent by weight sulfuric acid; and optionally, (B) up to 50 parts by weight of at least one of thermoplastic resins.

2. The fibers as claimed in Claim 1, wherein the poly(arylene thioether-ketone) has a density of at least 1.34 g/cm3 at 25°C when annealed at 280°C for 30 minutes.

3. The fibers as claimed in Claim 1, wherein the poly(arylene thioether-ketone) is an uncured polymer.

4. The fibers as claimed in Claim 1, wherein the poly(arylene thioether-ketone) is a polymer having a partially crosslinked and/or branched structure.

5. The fibers as claimed in Claim 1, wherein the thermoplastic material is substantially free of the thermoplastic resin.

6. The fibers as claimed in Claim 1, wherein the thermoplastic resin is a poly(arylene thioether) having predominant recurring units of the formula .

7. The fibers as claimed in Claim 1, wherein said fibers are stretched to a draw ratio of from 1.2:1 to 8:1.

8. The fibers as claimed in Claim 1, wherein the fibers have the following physical properties:
(a) density of portions of said poly(arylene thioether-ketone) being at least 1.34 g/cm3 at 25°C;
(b) tensile strength being at least 10 kg/mm2 at 23°C or at least 3 kg/mm2 at 250°C;
(c) tensile modulus being at least 100 kg/mm2 at 23°C or at least 30 kg/mm2 at 250°C;
(d) tensile elongation being at least 5% at 23°C; and (e) heat shrinkage (220°C/30 min) being at most 20%.

9. A process for the production of poly(arylene thioether-ketone) fibers, which comprises melt-extruding a thermoplastic material, which comprises:
(A) 100 parts by weight of a melt-stable poly(arylene thioether-ketone) having predominant recurring units of the formula , wherein the -CO- and -S- are in the para position to each other, and having the following physical properties (a) - (c):

(a) melting point, Tm being 310-380°C;
(b) residual melt crystallization enthalpy, .DELTA.Hmc (420°C/10 min) being at least 10 J/g, and melt crystallization temperature, Tmc (420°C/10 min) being at least 210°C, wherein .DELTA.Hmc (420°C/10 min) and Tmc (420°C/10 min) are determined by a differential scanning calorimeter at a cooling rate of 10°C/min, after the poly(arylene thioether-ketone) is held at 50°C for 5 minutes in an inert gas atmosphere, heated to 420°C at a rate of 75°C/min and then held for 10 minutes at 420°C; and (c) reduced viscosity being 0.3-2 dl/g as determined by viscosity measurement at 25°C and a polymer concentration of 0.5 g/dl in 98 percent by weight sulfuric acid; and optionally, (B) up to 50 parts by weight of at least one of thermoplastic resins at an extrusion temperature of 320-430°C through a spinneret, stretching the resultant fibers to a draw ratio of from 1.2:1 to 8:1 within a temperature range of 120-200°C, and then heat setting the thus-stretched fibers at 130-370°C for 0.1-1,000 seconds.

10. The process as claimed in Claim 9, wherein the poly(arylene thioether-ketone) has a density of at least 1.34 g/cm3 at 25°C when annealed at 280°C for 30 minutes.

11. The process as claimed in Claim 9, wherein the poly(arylene thioether-ketone) is an uncured polymer.

12. The process as claimed in Claim 9, wherein the polytarylene thioether-ketone) is a polymer having a partially crosslinked and/or branched structure.

13. The process as claimed in Claim 9, wherein the thermoplastic resin is a poly(arylene thioether) having predominant recurring units of the formula .

14. The fibers as claimed in Claim 9, wherein the fibers have the following physical properties:
(a) density of portions of said poly(arylene thioether-ketone) being at least 1.34 g/cm3 at 25°C;
(b) tensile strength being at least 10 kg/mm2 at 23°C or at least 3 kg/mm2 at 250°C;
(c) tensile modulus being at least 100 kg/mm2 at 23°C or at least 30 kg/mm2 at 250°C;
(d) tensile elongation being at least 5% at 23°C; and (e) heat shrinkage (220°C/30 min) being at most 20%.