JP2013249553A - Method for producing polyphenylene sulfide fiber - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a PPS fiber which is suitable for a nonwoven fabric that is applied to various filters such as a bag filter and a battery separator.SOLUTION: A method for producing the polyphenylene sulfide fiber comprises drawing an undrawn fiber at a drawing stress of 0.01-0.50 cN/dtex and a deformation velocity of 0.01-30.00 sso as to make a difference in double refraction be 10×10or more.

Description

  The present invention relates to a method for producing polyphenylene sulfide (hereinafter also referred to as “PPS”) fiber, which is suitable for producing a nonwoven fabric that can be developed on a filter or the like.

  While industrial sophistication advances, global warming is becoming more serious and interest in environmental destruction is spreading to the public. Against this background, not only developed countries but also developed countries have been required to have advanced performance in their processing equipment, such as regulations on exhaust gas. For this reason, as for the exhaust gas treatment device, a bag filter which exhibits a high dust collecting ability is becoming mainstream from the previous electric dust collector. A bag filter uses a cloth or non-woven fabric as a filter medium, which is made into a cylindrical shape and used for industrial dust collection. In this filter medium, fibers having excellent heat resistance and chemical resistance are used, and at the same time, there is an increasing demand for development of fibers used for the filters. At present, the fibers used in this filter medium include PPS fibers excellent in heat resistance, chemical resistance, and flame retardancy, and unmelted and insoluble polyphenylenesulfone fibers (PPSO) obtained by treating this PPS with an organic peroxide. Is the mainstream. Nonwoven fabrics made of PPS fibers and the like are expected to be used not only for bag filters but also for electrical insulating materials, paper making canvases, battery separators and the like by utilizing their characteristics. However, in these various filter applications, when the thickness is increased, the pressure loss when the fluid passes becomes excessive, and the efficiency of energy required for filtration is greatly reduced. For this reason, from the viewpoint of energy saving, the nonwoven fabric is required to be thin.

  From the viewpoint of making this thin film and exhibiting an advanced filter function, it is considered effective to reduce the fiber diameter of the PPS fibers constituting the nonwoven fabric, but PPS resins are compared to general-purpose resins such as polyester and polyamide, It is inferior in spinnability, and it is difficult to use a direct spinning method, a sea-island type, or a split type composite spinning method. On the other hand, there is a proposal relating to a technique of focusing on the drawing process and performing so-called super draw drawing by a liquid bath or the like to reduce the fiber diameter (Patent Documents 1 to 3).

In Patent Document 1 (pages 3 and 4), Patent Document 2 (pages 3 and 4) and Patent Document 3 (pages 3 and 4), a substantial (fiber) is maintained while maintaining the orientation state during spinning. A technical method is disclosed that utilizes the super-draw phenomenon in which the orientation of the structure is reduced without increasing the degree of orientation. Certainly, in this method, the thermal characteristics of the PPS resin and the deformation are completed within a very long deformation region called a liquid bath. Drawing is possible, and it can be said that this is an excellent technique for reducing the fiber diameter. However, in this super draw phenomenon, as symbolized by the fact that the orientation of the fiber structure does not increase, the drawing stress applied to the fiber during the drawing process is very unstable such that it is substantially zero. If thinning is manifested in the state, and excessively high-stretching is performed, as described in Patent Document 1, 0015, the quality deteriorates due to an increase in yarn breakage during the fiberizing process, and the cost increases due to a decrease in productivity. There is a problem. Actually, referring to the examples of Patent Documents 1 to 3, the range of the draw ratio being carried out is about 5 times at most, and even in view of the exemplified range in the specification, there is a limit to ultrafine PPS fibers. There was something. In addition, the drawn fiber that has been subjected to the super draw drawing treatment has a fiber structure (mechanical characteristics) that is substantially the same as that of the undrawn fiber, and only the fiber diameter is extremely thinned. However, it is difficult to say that it is easy to handle in subsequent post-processing steps such as general stretching and heat treatment. For this reason, it has been necessary to improve in consideration of process passability.

JP 2007-039840 A JP 2005-146427 A JP 2005-146428 A

  The subject of this invention is providing the manufacturing method of the ultra fine PPS fiber suitable for the nonwoven fabric applied to various filters, such as a bag filter and a battery separator.

  The above object is achieved by means having the following configuration.

(1) An unstretched fiber is made to have a birefringence difference of 10 × 10 ⁻³ or more at a stretching stress of 0.01 to 0.50 cN / dtex and a deformation rate of 0.01 to 30.00 s ^−1. A method for producing a polyphenylene sulfide fiber, which is drawn.

  Here, the “birefringence difference” means a difference between the birefringence of the stretched fiber and the birefringence of the unstretched fiber.

(2) The method for producing polyphenylene sulfide fibers according to (1), wherein the fibers are stretched so that the boiling water shrinkage of the fibers after stretching is 20% or more.

(3) The method for producing a polyphenylene sulfide fiber according to (1) or (2), wherein the unstretched fiber is heated by infrared light beam irradiation.

(4) The method for producing polyphenylene sulfide fiber according to (3), wherein the unstretched fiber is heated by irradiation with an infrared light beam using a carbon dioxide laser.

(5) The unstretched fiber is stretched at a stretch ratio of 10 times or more after being heated between a pair of rollers by irradiation with infrared rays using a carbon dioxide laser having a laser density of ² to 100 W / cm ² . (4) The manufacturing method of the polyphenylene sulfide fiber of.
It is.

  According to the production method of the present invention, it is possible to extremely finely form a fiber made of a PPS resin having low spinnability very stably. In addition, although the PPS fiber obtained by this production method is not substantially crystallized, the fiber structure is highly oriented, so that it has appropriate mechanical properties and a general drawing / heat treatment process. Even when it is introduced into a post-processing step including it, the handleability is good and the process passability is also excellent. Furthermore, highly oriented amorphous PPS fibers that could never be obtained by conventional methods have a wide range of applications. For example, fiber products such as non-woven fabrics can be used as long as they are not subjected to stretching and heat treatment processes. By performing heat treatment, it can be crystallized quickly and used as a PPS nonwoven fabric that can withstand practical use. In the PPS fiber manufactured by using the method of the present invention, heat treatment and the like are additionally performed, and free shrinkage is performed to control the basis weight of the nonwoven fabric to obtain a nonwoven fabric according to the application. Since it is oriented, it can be used as a PPSO fiber by treating with an organic peroxide.

It is a schematic structure diagram of the deformed fiber for explaining the deformation speed of the fiber. It is an enlarged view of the running yarn near the deformation point in the method for producing polyphenylene sulfide fiber according to one embodiment of the present invention. It is an enlarged view (with neck-like deformation) of a running yarn near a deformation point in a general fiber manufacturing method. It is an expanded sectional view which shows the example of the fiber which the defect (void) produced | generated.

  Hereinafter, the manufacturing method of the polyphenylene sulfide fiber which concerns on one embodiment of this invention is explained in full detail with desirable embodiment.

The PPS fiber production method of the present embodiment uses a PPS undrawn fiber produced by melt spinning as a draw stress of 0.01 to 0.50 cN / dtex and a deformation rate of 0.01 to 30.00 s ^−1. Is stretched so as to be 10 × 10 ⁻³ or more.

  PPS here means a polymer having phenylene sulfide units such as p-phenylene sulfide units and m-phenylene sulfide units as repeating units. Here, PPS may be a homopolymer composed of either a p-phenylene sulfide unit or an m-phenylene sulfide unit, or may be a copolymer having both. Further, other aromatic sulfides may be copolymerized within the range satisfying the object of the present invention.

  The molecular weight of the PPS resin used in this embodiment has an influence on the mechanical properties when fiberized. A non-woven fabric or the like is assumed as an application target of the present invention. In order to satisfy this practical characteristic, the range of the weight average molecular weight of the PPS resin to be used is preferably 30,000 to 70,000. In particular, the range of the weight average molecular weight in which the balance between the spinning property and the mechanical properties of the fiber is excellent is 40,000 to 60,000.

  In the production method of this embodiment, the PPS resin is made into unstretched fibers by an ordinary melt spinning method. That is, PPS pellets and the like are introduced into a melt extruder such as an extruder and melted, and a molten polymer weighed to a specified amount by a gear pump or the like is introduced into a spinning pack and discharged from the pores formed in the spinneret. Fiberize. Here, the melting (spinning) temperature may be set with reference to the melting point (Tm) of the PPS resin to be used + 10 ° C. or more. Since the melting point of a general PPS resin is 280 ° C., the spinning temperature is 290 ° C. to 340 ° C. If it is set in the range of ° C., fluidity suitable for melt spinning can be obtained. The pore diameter for discharging the melted PPS resin is generally selected between 0.2 and 3.0 mmφ in consideration of pressure loss and spinning draft (spinning speed / discharge linear speed). In general, the discharge hole is a round hole, but it may be a flat hole, a Y hole, a T hole or the like in consideration of passability such as post-processing as well as final use. .

The melted and discharged PPS resin is cooled and solidified by a cooling device such as Uniflow, and then an oil agent is applied and taken up by a roller. Here, it is taken up at a speed defined by a predetermined value by the circumferential speed of the take-up roller, and becomes an undrawn fiber used in this embodiment. If the peripheral speed of this roller, that is, the spinning speed is set to 100 to 1000 m / min, the fiber structure will not be excessively oriented on the spinning line, so that it becomes an unstretched fiber suitable for use in this embodiment. This unstretched fiber means a PPS fiber wound up by melt spinning, and means an unoriented amorphous PPS fiber that has not been substantially stretched and heat-treated. The term “unoriented” as used herein refers to a state defined by the fact that birefringence is less than 20 × 10 ⁻³ , and the value of birefringence is a letter using a polarizing microscope equipped with a Berek compensator. It can be calculated from the values of the foundation and fiber diameter. Moreover, the standard of the crystallinity for becoming amorphous is less than 15%, and the crystallinity is calculated by reading the low temperature crystallization peak and the melting peak from the DSC curve by differential scanning calorimetry (DSC). Can do. Incidentally, the degree of crystallinity = (heat of fusion−heat of crystallization) / heat of crystal fusion × 100 (%). Generally, the heat of crystal fusion of PPS may be calculated as 146.2 J / g.

In this embodiment, the unstretched fiber may be once wound on a drum or the like and then stretched as described later, or may be stretched continuously with the spinning step without being wound once. In this embodiment, the stretching step is important, and in particular, it is important to stretch the film at a stretching stress of 0.01 to 0.50 cN / dtex and a deformation rate of 0.01 to 30.00 s ⁻¹ .

  The deformation speed here means a change in speed per unit distance. That is, when the fiber speed at the deformation start position (1) shown in FIG. 1 is V1, the fiber speed at the deformation end position (2) is V2, and the distance between the deformation start position and the deformation end position is L, The deformation speed can be obtained from the equation [deformation speed = (V2−V1) / L]. In addition, in order to simplify description regarding this deformation | transformation speed, although demonstrated using the speed difference between a deformation | transformation start position (1) and a deformation | transformation end position (2), the measurement of a deformation | transformation speed is measuring the fiber. If it is a section, it may be taken anywhere. Actually, as illustrated in FIG. 2, it can be calculated by photographing a fiber with a CCD (Charge Coupled Device) camera or the like and processing the image. That is, if the fiber diameter and the fiber speed are known in advance, the speed and distance between arbitrary positions in the image can be measured. Using this parameter, the above-described equation [deformation speed = ( The deformation speed can be calculated based on V2-V1) / L]. In the present embodiment, the position and speed of an arbitrary 10 locations were measured from the image obtained by photographing the deformation section, and were obtained by rounding off the third decimal place of the simple average of the deformation speed calculated as n number 5.

In the present embodiment, it is important that the deformation speed is 0.01 to 30.00 s ⁻¹ , and a numerical range completely different from the conventional method is adopted. That is, not only the PPS fiber but also the so-called unstretched fiber is stretched because the fiber structure is unoriented. Therefore, when the deformation is started, the deformation locally occurs and the neck as shown in FIG. Cause deformation. In this case, the orientation of the fiber structure increases rapidly, and a high degree of orientation can be imparted. However, in the case of the PPS fiber, the fiber cannot follow the rapid deformation, and the stress is locally applied in the cross-sectional direction of the fiber. As a result of the occurrence of concentrated locations, defects (voids) are generated in the fiber cross section (see FIG. 4), and high-stretching cannot be performed. Further, in this case, the mechanical properties are also lowered, so that it is more difficult to stretch at a high magnification, which becomes a high stress. Incidentally, in the case of neck-shaped deformation as illustrated in FIG. 3, the deformation speed of the fiber referred to in this specification is at least 100.00 s ⁻¹ or more, which is a completely different numerical range from the main deformation speed. On the other hand, using a liquid bath or the like to cause a super draw phenomenon and reduce the deformation speed is a known technique. This is by utilizing the plasticizing effect due to heat and moisture by stretching in a liquid bath, and since the deformation is performed using the full length of the liquid bath, it suppresses the generation of the aforementioned voids, It is possible to stretch at a high magnification to a certain extent. However, in this method, as described in Patent Documents 1 to 3, since only the fiber diameter is reduced while the fiber is substantially unstretched, the mechanical properties of the fiber remain low and the liquid bath is running. Since it is subjected to fluid resistance, the running yarn tends to break. For this reason, as can be seen from the examples of Patent Documents 1 to 3, there is a limit to the draw ratio that can be reached, that is, ultrathinning. Moreover, even if the liquid bath is luckily passed safely, the influence of rubbing with a roller or the like and a droplet taken out of the liquid bath cannot be ignored. As long as a liquid bath or the like is used, in order to cause the super draw phenomenon to occur, a heating time (distance) of a certain degree or more is necessary, and the deformation section naturally becomes longer. Less than 001 s ⁻¹ , significantly below the range of this embodiment. In this case, the desired stretch stress range cannot be satisfied, and the running yarn becomes unstable, and above all, it does not become a highly oriented amorphous PPS fiber that is important in the post-processing property of the present invention.

As a result of intensive investigations on the deformation rate for drawing the PPS fiber, the inventors have first determined that the deformation rate is 0.01 to 30.00 s ⁻¹ in order to satisfy the object of the present invention. I found out. In other words, the inventors have found that the high-strength drawing that cannot be achieved by the conventional method can be stably performed by utilizing the phenomenon that the mechanical properties of the running yarn are expressed due to the high orientation of the fiber structure. In consideration of the stability of the running yarn, a more preferable range of the deformation speed is 0.01 to 15.00 s ⁻¹ , and the ultrafine PPS fiber having a fiber diameter of micron order is obtained by increasing the draw ratio to 100 times or more. It can be manufactured with good processability.

  In addition to the above control of the deformation rate, in the present embodiment, it is important to control the stretching stress within the range of 0.01 to 0.50 cN / dtex. This contributes to high orientation of the fiber structure while maintaining an amorphous state that could not be obtained by the conventional method. That is, by setting the stretching stress to 0.50 cN / dtex or less, rapid orientation of the fiber structure can be suppressed without causing neck-like deformation as shown in FIG. On the other hand, highly oriented amorphous PPS fibers can be produced by gently orienting the fiber structure by making the stretching stress 0.01 cN / dtex or more.

  The term “stretching stress” as used herein means the stress per unit cross-sectional area of the drawn fiber, and can be calculated by dividing the drawing tension measured with a contact-type yarn tension measuring machine by the fineness after drawing. In this embodiment, this stretching tension was measured with an n number of 5, and was obtained by rounding off the third decimal place of the simple average of the values divided by the average fineness of the drawn fibers. From the viewpoint that the running yarn travels more stably, it is more preferable to set the stretching stress to 0.01 to 0.20 cN / dtex. In addition, ultra fine PPS fibers can be produced stably.

In this embodiment, it is important in the production method of this embodiment that the fiber structure is oriented to such an extent that birefringence increases by 10 × 10 ⁻³ or more before and after stretching. The birefringence referred to here is calculated from the values of retardation and fiber diameter using a polarizing microscope equipped with a Belek compensator. In the present embodiment, the birefringence of the fiber was measured by setting the number of n to 5, and calculated by rounding off the fourth decimal place from the simple average. Here, the birefringence difference in this specification refers to the difference between the birefringence of the drawn fiber and the birefringence of the unstretched fiber obtained by birefringence measurement regarding the undrawn fiber and the drawn fiber. If this birefringence difference is 10 × 10 ⁻³ or more, it means that the fiber structure is oriented, and is manifested as a significant difference in mechanical properties (for example, strength), resulting in the effect of improving the passability of the stretching process and the like. Let In particular, when the birefringence difference is 20 × 10 ⁻³ or more, since the strength is improved by about 0.5 cN / dtex before and after stretching, the stability of the running yarn can be improved. Although there is no particular upper limit to the birefringence difference, a birefringence difference of 150 × 10 ⁻³ is substantially required to produce an amorphous PPS fiber that is highly oriented, which is the target of the production method of this embodiment. Can be cited as an upper limit.

  Assuming that the highly oriented amorphous PPS fiber thus produced is finally made into a non-woven fabric or the like and made into a fiber product, here, it is necessary to adjust the weight per unit when the structure of the fiber structure is fixed. Therefore, it is preferable to have a property of contracting when heated. As a measure of such characteristics, the PPS fiber produced by the method of this embodiment preferably has a boiling water shrinkage of 20% or more. In such a range, in the case of a non-woven fabric, it is possible to control shrinkage while ensuring a relatively large degree of freedom in heating temperature and processing time, in addition to being able to realize various forms of textile products. It can also be used as a binder fiber. In obtaining the boiling water shrinkage referred to here, first, the skein length is measured using a measuring machine to make the fibers small. Subsequently, the skein is treated with boiling water at 98 ° C. for 10 minutes, and the skein length is measured again after air drying. From the skein length before treatment and the skein length after treatment, the boiling water shrinkage rate is calculated using the following formula: [Boiling water shrinkage rate = (before treatment skein length−after treatment skein length) / pretreatment skein length × 100 (%)]. The In this embodiment, the boiling water shrinkage was calculated with n = 5, and the simple average of the calculation results was rounded off to the second decimal place. The boiling water shrinkage can be controlled by adjusting the stretching stress according to the final application, but the substantial upper limit is 50%.

  In the present specification, stretching refers to an operation of stretching and deforming fibers in the fiber axis direction at a peripheral speed ratio of each roller between a pair of stretching rollers as in a normal stretching step.

  In the stretching of this embodiment, it is necessary to heat the unstretched fiber to the softening point or higher, and thus it is necessary to heat-stretch. The heat drawing here can also be performed by a contact heating method such as a roller, a hot plate, a heat pin or the like heated to a temperature higher than the glass transition temperature of the PPS undrawn fiber. However, from the viewpoint of uniform stretching, it is preferable to use a non-contact heating method such as infrared light beam irradiation. This is because, in the case of the contact heating method, the stress may change on the surface in contact with the roller or the like, so the non-contact method is suitable for realizing uniform stretching. In the case of irradiating the infrared light beam between the drawing rollers, the single fiber and the fiber bundle are heated extremely uniformly by radiant heating, and the unique phenomenon of this embodiment can be expressed uniformly without variation. From the above viewpoint, it can be said that thermal stretching using a non-contact heating method by infrared light beam irradiation is suitable for the manufacturing method of this embodiment. Infrared here means an electromagnetic wave having a wavelength in the range of 1 to 100 μm, longer in wavelength than red visible light, and shorter in wavelength than radio waves. According to this infrared light beam irradiation, the yarn temperature can be raised in a short time, and the local region can be rapidly heated. Therefore, it is particularly suitable for controlling the deformation speed. Moreover, since this heat drawing method also has the side surface with the high transmittance | permeability with respect to PPS fiber, it is suitable for uniform drawing also at the point which can raise the temperature of the cross section of a single fiber and a fiber bundle uniformly.

  In this embodiment, the infrared light beam irradiation is specifically performed using a halogen lamp or a laser light source. Among these, it is preferable to use laser light because it is monochromatic light and has high energy. Among these, it is more preferable to use a carbon dioxide laser (wavelength 10.6 μm) because continuous oscillation, long-time use is possible, high output can be obtained, and it is relatively inexpensive.

In the stretching process in this embodiment, when the traveling yarn is irradiated with laser light and energy necessary for deformation is accumulated, the deformation is started by the stretching stress. The laser light irradiation conditions in this embodiment are preferably determined from the fineness of undrawn fibers (thickness of single fibers, the number of filaments), the drawing speed, and the like, but generally the laser density should be 2 W / cm ² or more. Stretching can be started. On the other hand, if the laser density is 1000 W / cm ² or less, undrawn fibers having an undeveloped fiber structure can be continuously produced without causing fusing. In order to suppress fusing and the like in this embodiment, the laser density is more preferably ² to 100 W / cm ² . Specifically, the laser spot diameter is preferably 0.1 to 20.0 mm. In general, laser light has a Gaussian distribution within a spot, and the laser density differs greatly between the outermost layer and the innermost layer of the spot. For this reason, when the spot diameter is 0.2 to 10.0 mm, deformation can be started stably from a portion where the laser energy of the inner layer is strong. When irradiating a laser beam, a method of specular reflection, a method of condensing various lenses (for example, a cylindrical lens), a method of installing a laser oscillator away from the yarn by an optical fiber, etc. are used. Is possible. The laser beam may be irradiated only from one side, but in the case of a multifilament or a monofilament having a large fiber diameter, it is preferable to irradiate the laser beam from multiple directions from the viewpoint of fixing the drawing point. As described above, the laser light irradiation conditions are preferably determined in consideration of the type of unstretched fibers and the stretching conditions. In order to perform a drawing process at a higher speed from the viewpoint of improving productivity, since the temperature rise to a temperature range above the softening temperature that triggers plasticization becomes the rate-determining method, it is preliminarily heated below the glass transition temperature of the undrawn fiber. It is also preferable to do.

  In the production method of this embodiment, the draw ratio can be easily increased. For this reason, it is possible to easily produce ultrafine fibers excellent in post-processability made of a PPS resin that is inferior in spinnability and stretchability as compared with general-purpose resins such as polyester and polyamide. The draw ratio can be adjusted from the fiber diameter required for the final product. From the viewpoint of obtaining ultrafine PPS fibers, the draw ratio is preferably 10 times or more. Although there has never been a drawing method that can set the draw ratio to 10 times or more, an excellent ultrafine PPS fiber can be obtained by this application. Considering the familiarity when the fiber diameter is reduced and treated with an organic oxidizing agent or binder fiber, the fiber diameter is preferably set to several μm. On the other hand, considering that it is difficult to reduce the fiber diameter in the spinning process, it is preferable from the viewpoint of productivity that the fiber diameter is reduced by the drawing process of the present embodiment, so in this specification. It is more preferable to set the draw ratio to 50 times or more. In this case, since the advantage of the present invention can be used more effectively as the draw ratio is higher, the draw ratio is particularly preferably 100 times or more.

  The PPS fiber obtained by the production method of this embodiment preferably has a strength of 1.0 cN / dtex or more in consideration of the stability of the running yarn in the drawing process. From the viewpoint of enhancing the process passability in post-processing, the strength is more preferably 2.0 cN / dtex or more. Further, for the purpose of the present invention, it is preferable that the fiber diameter of the single PPS fiber to be collected is 30 μm or less, and in order to effectively use the features of the present invention, the fiber diameter is 10 μm or less. More preferred. With respect to the production method of this embodiment, the fiber diameter can be made extremely small, but considering the handleability in post-processing, the practical lower limit is about 0.1 μm. Incidentally, when converted into the fineness of the single fiber, the preferred range corresponds to 0.0001 to 10 dtex.

  Hereinafter, the manufacturing method of the polyphenylene sulfide fiber which concerns on the embodiment of this invention is demonstrated still in detail using an Example. The following methods were used as various measurement methods in the examples.

A. Deformation speed during the drawing process Between the pair of drawing rollers, the running yarn in the deformation section was photographed with a Victor TK-C1461 CCD camera equipped with an OPTAR TV-1M telecentric lens. The fiber diameter and the distance between two points are measured for the points. The speed difference and deformation distance of the running yarn are calculated from the measured values, and the deformation speed is calculated from the relational expression [deformation speed = speed difference / deformation distance]. The same operation was performed with n as 5, and the simple average value was rounded off to the third decimal place. The deformation section here means a section in which the fiber diameter of the traveling yarn is deformed (reduced) stepwise with the traveling distance.

B. Stretching stress during the stretching process The stretching tension of the running yarn is measured with a tension meter HS-1500S manufactured by Eiko Sokki Co., Ltd. at an arbitrary position downstream of the deformation section between the pair of stretching rollers. The stretching tension was taken into a personal computer with a sampling interval of 100 ms using NR-200 manufactured by KEYENCE, and the average value of n number 100 was measured. The value obtained by dividing this by the fineness after stretching was defined as the stretching stress, and the n number was 5. Rounded down to the third decimal place of the simple average. The arbitrary position downstream from the deformation section here means an arbitrary position downstream from the point at which the deformation of the fiber diameter of the traveling yarn ends.

C. Birefringence difference in fiber birefringence and drawing The retardation and path length of a single fiber are measured with an OLYMPUS BH-2 polarizing microscope to determine birefringence. Regarding birefringence, each fiber was measured with an n number of 5, and rounded off to the fourth decimal place of the simple average. This birefringence measurement is performed on unstretched fibers and stretched fibers, and the difference between the birefringence of the stretched fibers and the birefringence of the unstretched fibers is defined as the birefringence difference.

D. Fiber crystallinity DSC curve was measured using TA Instruments DSC2920 Modulated DSC, low temperature crystallization peak and melting peak were read from the profile, and [crystallinity = (heat of fusion−heat of crystallization) / crystal fusion] The crystallinity of the fiber is calculated from the equation of “heat × 100 (%)”. Here, the heat of crystal fusion of PPS was calculated as 146.2 J / g. The crystallinity of the fiber was calculated by setting the number of n to 5, and the simple average value was rounded off to the second decimal place.

E. Single yarn fiber diameter Ten fibers arbitrarily selected from the images taken with a VE-7800 SEM manufactured by Keyence Co., Ltd. at a magnification that allows observation of five or more fibers, with the fibers before or after stretching as small pieces. The diameter of a single fiber is measured two-dimensionally using image processing software (WINROOF). The ten points in the image were obtained by rounding off the first and second decimal places of the simple average of the diameter of the single fiber measured in μm.

F. Fineness of a single fiber In an atmosphere controlled at 25 ° C. and 55% RH, the fiber is made a small portion of 100 m with a measuring machine, and the value obtained by multiplying the weight by 100 is defined as the total fineness. The fineness of a single fiber is calculated by dividing the total fineness by the number of filaments. In addition, the fineness of this single fiber was measured by setting the n number to 5, and rounded off to the third decimal place of the simple average.

G. Fiber mechanical properties (strength, elongation)
Under an atmosphere controlled at 25 ° C. and 55% RH, the initial sample length is set to 200 mm, the pulling speed is set to 100% mm / min, and a load-elongation curve is obtained under the conditions shown in JIS L1013 (1999). Next, the load value at the time of fracture is divided by the initial fineness, which is used as the strength, and the elongation at the time of fracture is obtained as the elongation by the initial sample length. The same evaluation was carried out with n = 10, and the simple average was obtained. For strength, the value rounded to the second decimal place was rounded off, and for elongation, the decimal point was rounded off.

H. Boiling water shrinkage rate of fibers To determine the boiling water shrinkage rate, first we measure the length of the skein using a measuring machine. Subsequently, the skein is treated with boiling water at 98 ° C. for 10 minutes, air-dried, and the skein length is measured again. Based on the skein length before treatment and the skein length after treatment, the boiling water shrinkage rate is calculated using the following formula: [boiling water shrinkage rate = (pretreatment skein length−post treatment skein length) / pretreatment skein length × 100 (%)]. . The boiling water shrinkage was calculated with the n number being 5, and the simple average of the calculation results was rounded off to the second decimal place in percent.

Example 1:
The dried PPS chip (weight average molecular weight 45000) was dried with a vacuum dryer so that the moisture content of the chip was 300 ppm or less, and charged in a hopper as a nitrogen atmosphere. The chips were melted while measuring the amount of chips in a twin-screw melt extruder (30 mmφ, L / D = 42) installed under the hopper. The screw rotation speed of the twin-screw extrusion kneader was 100 rpm, venting was performed on the discharge side of the twin-screw extrusion kneader to deaerate, thereby eliminating the bubbles and discharging the moisture generated during the extrusion kneading.

The spinning temperature (kneading machine and spinning head) was 330 ° C., filtered through a metal non-woven fabric with an absolute filtration diameter of 10 μm, and the discharge rate was 3.0 g / min with a die (discharge hole diameter: 0.5 mmφ, discharge hole length / discharge hole diameter) (L / D) = 5, 1-hole) was melted and discharged, passed through a uniflow cooling air zone, and then an oil agent was adhered to obtain an undrawn PPS fiber at a spinning speed of 200 m / min. This unstretched PPS fiber had a single yarn fineness of 153 dtex (fiber diameter of 120 μm), a birefringence of 9.0 × 10 ⁻³ , and a crystallinity of 6.0%.

This unstretched PPS fiber was stretched using a laser stretching machine equipped with a carbon dioxide laser irradiation device between a pair of rollers. Undrawn fiber was supplied at a feed speed of 0.5 m / min by a supply roller equipped with a nip roller. The supplied unstretched fiber passed through a laser (irradiation) spot and was wound up with a stretching roller so that the stretching ratio was 200 times. In this example, the yarn was threaded at a low draw ratio of 1.2 times, and then the speed of the drawing roller was gradually increased to develop the characteristic drawing phenomenon of this embodiment. In addition, the laser irradiation device is equipped with a three-way irradiation system using a reflecting mirror, and a laser density of 45 W / cm ² (laser output 9.0 W, spot diameter 5 mmφ) is irradiated with this device. The PPS fiber was plasticized and stretched. Incidentally, although this sampling was carried out for about 1 hour, the yarn was not broken and had a very stable stretchability.

The deformation speed of this laser spot (deformation section) was 15.00 s ⁻¹ and the stretching stress was 0.40 cN / dtex. The birefringence difference in this stretching is 80 × 10 ^−3, and the crystallinity is 11.0% despite the highly oriented fiber structure after stretching, which is an unprecedented highly oriented amorphous PPS. The fiber was successfully collected. Further, the fiber diameter and mechanical properties of the obtained PPS stretched fiber are as shown in Table 1. Since the fiber structure is oriented even though it is highly refined, it has excellent mechanical properties. I had it.

Examples 2-4:
Using the unstretched PPS fibers used in Example 1, the draw ratio was set to 100 times (Example 2), 10 times (Example 3), and 5 times (Example 4), and the laser density was set to Table 1. The film was stretched by changing as described in. The laser density was controlled by changing the laser power.

  In any case, as in Example 1, it had a stable stretchability without breakage. The physical properties of the drawn fibers are as shown in Table 2. The fiber diameter is reduced with the draw ratio, and the birefringence increases despite the fact that the crystallinity does not change substantially. Crystalline PPS fibers could be produced.

Examples 5-6:
Using the PPS resin used in Example 1, without changing conditions such as spinning temperature, a die having 50-hole pores (discharge hole diameter: φ0.3 L / D = 2.0) After being discharged at a total discharge amount of 10 g / min, undrawn PPS fibers were obtained at a spinning speed of 1000 m / min.

The unstretched PPS fiber had a single yarn fineness of 2 dtex (fiber diameter of 13.7 μm), a birefringence of 11.0 × 10 ⁻³ , and a crystallinity of 9.0%. Except that this unstretched fiber was used and stretched under the conditions described in Table 1, all followed Example 1.

  The PPS fibers obtained in this example were highly oriented amorphous as in Example 1. Particularly in Example 5 in which the draw ratio was 200 times, the single yarn fiber diameter was reduced to 1.0 μm, but it had relatively high mechanical properties and was excellent in handling. It was.

Comparative Example 1:
The undrawn PPS fiber used in Example 1 was stretched using the super draw phenomenon due to the liquid bath. The stretching device used in this comparative example was stretched by a pair of rollers as in Example 1, and a liquid bath was installed between the rollers. The fiber supplied at 0.5 m / min by the supply roller passes through the liquid bath and is drawn by the speed difference between the supply roller and the drawing roller. The temperature of the liquid bath was adjusted to 90 ° C., and a liquid bath having a length of 500 mm was used.

In this comparative example, the entire liquid bath is the deformation section, the deformation rate is very low as less than 0.001 s ⁻¹ , and the stretching stress and birefringence difference are very low as compared with the manufacturing method of this embodiment. there were. In this comparative example, since the drawing stress (tension) was too low, the drawing state such as slackening of the yarn under the influence of water droplets adhering to the running yarn after leaving the liquid bath was unstable. For this reason, the limit of the draw ratio that can be reached is 5 times.

When the collected drawn fibers were confirmed, the birefringence was 12 × 10 ⁻³ and the fiber structure was not oriented, so the strength was 0.7 cN / dtex, which was unchanged from the value of undrawn fibers. The results are shown in Table 2.

Comparative Example 2:
Using the unstretched PPS fiber used in Example 1, stretching was performed utilizing neck deformation caused by laser irradiation. In this comparative example, using the same drawing apparatus as in Example 1, the draw ratio was set to a high magnification so that neck-shaped deformation was manifested.

When the deformation section of Comparative Example 2 was confirmed, a very sharp neck-shaped deformation portion was generated at the laser irradiation position. Here, the deformation speed was 536.00 s ⁻¹ , and it was found that the film was stretched at a deformation speed of 10 times or more as compared with the Examples. In addition, when the running yarn of this comparative example was observed, it became cloudy after extending | stretching, and when the cross section of the stretched fiber was confirmed by SEM, it was confirmed that innumerable voids were producing | generating. By the way, in the drawing mode that generates this neck-like deformation, the upper limit of the draw ratio is 4.5 times, and even when the draw ratio is 4.5 times, yarn breakage occurs in a short time sampling. The results are shown in Table 2.

Comparative Example 3:
Using the unstretched PPS fiber used in Example 1, stretching was performed with a normal heating roller. In this comparative example, using the same apparatus as in Example 1, instead of performing laser irradiation, stretching was performed by bringing a hot plate (length: 300 mm) heated to 90 ° C. into contact with the running yarn.

In this comparative example, it was confirmed that neck-shaped deformation was developed on the hot plate, and the deformation speed here was 333 s ⁻¹ . In this comparative example, the running yarn became cloudy as in Comparative Example 2, and it was confirmed that countless voids were generated when the cross section of the drawn fiber was confirmed by SEM. Incidentally, the upper limit of the draw ratio in the drawing form using a hot plate as in this comparative example was 3.5 times. The results are shown in Table 2.

  The method for producing polyphenylene sulfide fibers according to the present invention can be widely used for producing nonwoven fabrics that can be developed on filters and the like.

DESCRIPTION OF SYMBOLS 1 Deformation start position 2 Deformation end position 3 Deformation distance 4 Fiber 5 Neck-shaped deformation part 6 Void

Claims (5)

The unstretched fiber is stretched so that the birefringence difference is 10 × 10 ⁻³ or more at a stretching stress of 0.01 to 0.50 cN / dtex and a deformation rate of 0.01 to 30.00 s ^−1. A process for producing polyphenylene sulfide fibers characterized by the above.   The method for producing a polyphenylene sulfide fiber according to claim 1, wherein the stretched fiber has a boiling water shrinkage ratio of 20% or more.   The manufacturing method of the polyphenylene sulfide fiber of Claim 1 or 2 which heats the said unstretched fiber by infrared rays light beam irradiation.   The manufacturing method of the polyphenylene sulfide fiber of Claim 3 which heats the said unstretched fiber by infrared rays light beam irradiation using a carbon dioxide laser. The unstretched fiber is stretched at a stretch ratio of 10 times or more after being heated between a pair of rollers by irradiation with an infrared light beam using a carbon dioxide laser having a laser density of ² to 100 W / cm ^2. The manufacturing method of the polyphenylene sulfide fiber of description.

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