JP3003155B2 - Method for producing high-strength high-modulus polyester fiber - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for industrially producing a polyester fiber having unprecedented high strength and high elasticity. More particularly, the present invention relates to a method for producing a high-performance polyester fiber useful for a tire reinforcing material, a conveyor belt reinforcing material, a thermoplastic composite reinforcing material, and the like.

(Prior Art) Conventionally, methods for obtaining high-strength, high-modulus polyester fibers include, for example, JP-A-63-12715 and JP-A-63-99322.
JP-A-63-196711, JP-A-63-196712, JP-A-63-196713, and the like have been proposed.
Use of a raw material polymer having a high degree of polymerization as a means for obtaining a polyester fiber having a high strength and a high elastic modulus common to these patents is in principle the right direction. Research based on this concept has been conventionally performed, and recent advances in polymerization technology have made it possible to industrially obtain ultrahigh molecular weight polyethylene terephthalate having an intrinsic viscosity exceeding 3.0.

(Problems to be Solved by the Invention) However, looking at the above-mentioned prior art, when trying to obtain a high-performance fiber by a melt spinning method using ultrahigh molecular weight polyethylene terephthalate, the melt viscosity is extremely high because of the ultrahigh molecular weight material. The spinning with the conventional spinning apparatus, method and conditions is extremely difficult because the temperature becomes high and the fluidity of the melt is extremely reduced. Therefore, JP-B-47-3372 and USP384
As shown in 6377, a spinning device that can withstand high pressure has been newly designed.Spinning research under high pressure and high temperature has also been conducted, but the equipment investment of the device is large due to the application of pressure resistance, and the productivity is also reduced by such a method. Is unavoidable and is not sufficiently practical. According to the technique described in JP-A-61-207616, spinning is carried out at a dilute concentration of 3 to 10% by weight using a solution for processing a highly polymerized polyester. It is not practical considering the low cost and solvent recovery cost. JP-A-63-1271
No. 5 discloses a high-strength high-modulus polyester fiber obtained by dissolving an ethylene terephthalate-based polyester having an intrinsic viscosity of 1.2 or more in a mixed solvent of trifluoroacetic acid and methylene chloride to form a stock solution for spinning and thermally drawing an undrawn yarn obtained therefrom. Although a manufacturing technique is disclosed, this also has a problem in productivity as in the above patent. Further, in the technique described in JP-A-63-196712, it is necessary to extremely reduce the shearing speed at the nozzle orifice, and therefore, the spinning speed must be applied at a very low spinning speed of at most 20 m / min. Low productivity and lacks practicality. JP-A-63-196711
The technology described in JP-A-63-196712 is a technology obtained by adding a technology of swelling using a solvent such as acetone before stretching to the technology described in JP-A-63-196712. Lack of practicality in terms of sex. As described above, none of the production methods can be said to have sufficient practicality, and at present, high performance polyester fibers having high strength and high elastic modulus have not been industrially obtained.

All of the conventional techniques for obtaining high-strength, high-modulus polyester fibers lack practicality and are difficult to employ in industrial-scale production. This invention solves the problem of practicality, especially high-speed productivity, which was lacking in the prior art with respect to high strength and high elastic modulus of ethylene terephthalate-based polyester fiber, and enables stable spinning and drawing of high-strength high-modulus polyester fiber. To provide a new manufacturing method.

(Means for Solving the Problems) Means for solving the above-mentioned problems, that is, the present invention provides an ethylene terephthalate polyester having an intrinsic viscosity (IV) of 1.0 to 3.0 at a temperature of 210 ° C. or more. 2 to 50% by weight of the compatible compound is added to the ethylene terephthalate-based polyester, melted and extruded from a nozzle orifice, and then the spun yarn is cooled and solidified and taken off, continuously or once after spinning. This is a method for producing a high-strength, high-modulus polyester fiber, which comprises winding and then stretching.

The ethylene terephthalate polyester used in the present invention has an intrinsic viscosity of 1.0 or more and less than 3.0 and at least 85 mol%
Of ethylene terephthalate unit. 3.Intrinsic viscosity is 3.
In the case of 0 or more polyesters, even if the compound compatible with the polyester is added, the melt viscosity of the melt is high. Therefore, in order to fiberize by the melt spinning method, a special spinning device with a high pressure resistance specification and a special spinning and drawing are used. Conditions are required, the limiting viscosity is 1.0
This is because if the polyester is less than the above, the high strength and high elastic modulus characteristic of the fiber of the present invention cannot be obtained. The ethylene terephthalate-based polyester of the present invention is most preferably polyethylene terephthalate alone for the purpose of obtaining high-strength, high-modulus fibers, but must be a polyester composed of at least 85 mol% of ethylene terephthalate. In the present invention, the compound which is added to the ethylene terephthalate-based polyester and is compatible with the polyester is at least one compound selected from a biphenyl compound, a naphthalene compound or a phenyl ether compound, or a mixture thereof. By adding the compound to the ethylene terephthalate-based polyester, the magnitude of the decrease in melt viscosity in the molten state and the degree of improvement in the thermal stability (retention of intrinsic viscosity) of the polyester polymer, and further, the compound and the compound were added. Particularly preferred compounds in consideration of the handleability of the polyester polymer and the like include ethyl biphenyl, 1-methylnaphthalene, diphenyl ether, and the like. The addition ratio of these compounds to the polyester polymer is 2% by weight or more,
Less than 50% by weight, more preferably 2 to
20% by weight. If the addition ratio of the compound to the polyester polymer is less than 2% by weight, a melt viscosity satisfactory in the present invention cannot be obtained. Further, as described later, high draw ratio cannot be achieved with an undrawn yarn obtained by spinning the polyester. . On the other hand, if the addition ratio of the compound to the polyester polymer exceeds 50% by weight, the amount of the added compound from the spun yarn is remarkably increased when the mixed polymer is discharged from the nozzle orifice. A solvent recovery device is required from the viewpoint of the working environment. This should be defined as dry spinning rather than melt spinning, which will dramatically increase the manufacturing costs of the device. Since the present invention employs a melt spinning method to achieve high strength and high modulus at low cost, it does not meet the purpose. Further, problems arise in terms of operability such as spinneret stains. There is no particular limitation on the method of adding the compound compatible with the ethylene terephthalate-based polyester to the polyester polymer, but the polyester polymer and the compound are mixed in advance in a stirring and mixing apparatus, and a molten mixture of the polyester polymer and the compound is mixed. A method of forming chips after cooling, a method of quantitatively supplying the compound from a raw material supply unit of a melt spinning device, and mixing in an extruder can be employed. The polyester polymer to which the compound has been added is melted and extruded at a temperature higher than the melting point of the compatible compound, preferably at least 10 ° C. higher than the melting point of the mixture. It is particularly noteworthy that the ethylene terephthalate-based polyester containing the compound exhibits a melting point drop in the range of 10 to 50 ° C., depending on the addition ratio, as compared to the ethylene terephthalate-based polyester not containing the compound. . This means that melt extrusion can be performed at a temperature lower than that of a polyester polymer to which the compound is not added by an amount corresponding to a decrease in melting point, and thermal breakage of molecular chains can be suppressed. Thus, the addition of the compound has the advantage of lowering the melt viscosity and thereby improving the processability of the polymer, that is, has the advantage of suppressing the thermal decomposition by lowering the melt extrusion temperature at the same time as the viscosity reducing effect. The melt extrusion method is not particularly limited, but an extruder type extruder, a piston type extruder, a twin-screw kneading type extruder, or the like is used. In this way, the ethylene terephthalate-based polyester spun yarn discharged from the nozzle orifice after melting is solidified by cooling, and an appropriate amount of an oil agent is applied as necessary, and the birefringence Δn of the yarn becomes 0.0001 to 0.0200. To take over.
When the birefringence of the drawn undrawn yarn is 0.0200 or more, the effect of increasing the drawability due to the addition of the compound becomes small, and it becomes difficult to achieve high strength and high elastic modulus. On the other hand, when the birefringence is less than 0.0001, the spinning state becomes extremely unstable, and it becomes difficult to suppress unevenness in the longitudinal direction of the yarn generated in the spinning process. After the wound yarn is wound once or continuously with the spinning, the yarn is drawn at a temperature higher than the glass transition temperature of the undrawn yarn at a draw ratio higher than the natural draw ratio. It should be noted here that the melt-spun yarn according to the present invention usually has the compound remaining in the yarn, and thus has a lower glass transition temperature than that of the polyester alone. When the stretching temperature is lower than the glass transition temperature, the mobility of the molecular chains is not sufficient, the alignment of the molecular chains by stretching is low, and it is difficult to increase the stretchability in the next stretching step. When the first-stage stretching is less than the natural stretching ratio, the frequency of yarn spots increases in the process,
No improvement in stretchability can be expected in the next stretching step, and the total draw ratio does not increase. Following the first stage stretching, 150-250 ° C
The next stage of stretching is carried out within the temperature range described above. If necessary, the film may be stretched in multiple stages, but it is important that the film is stretched at a maximum stretching stress of 3.0 g / d or more in the final stretching step. When the film is stretched under a stress of less than 3.0 g / d, it is difficult to achieve the high strength and high elastic modulus aimed at by the present invention. The drawing conditions for obtaining the drawing stress include the addition rate of the compound and the diffusion rate of the compound inside the yarn, the evaporation rate from the yarn surface and the yarn temperature during drawing, the residence time at that temperature, and the like. Determined by taking into account. One of the technical points is how to add the compound to increase the inter-entanglement distance between the molecular chains of the polyester and to reflect the effect of increasing the natural stretch ratio on the increase in the total stretch ratio. By multi-stretching the undrawn yarn containing the compound under specific conditions as described above, the total draw ratio of the undrawn yarn is dramatically increased, and the practical use of a high-strength high-modulus ethylene terephthalate-based polyester fiber is practical. Manufacturing becomes possible.

Hereinafter, methods for measuring various characteristic values used in the evaluation of the present invention will be described.

<Measurement Method of Melt Viscosity> Using an extruder-type extruder, melt-discharge from a nozzle orifice maintained at a constant temperature through an ethylene terephthalate-based polyester, and discharge the hole diameter, hole length, and single hole of the nozzle orifice. Shear stress and shear rate were calculated from the amount and discharge pressure to determine the melt viscosity of the polymer. The viscosity obtained by extrapolating the shear rate to zero was regarded as zero shear viscosity (η _o ) at the measurement temperature.

<Measurement Method of Intrinsic Viscosity> In the present invention, the intrinsic viscosity (IV) of the ethylene terephthalate-based polyester is measured by using a mixed solution of P-chlorophenol / tetrachloroethane = 3/1 at a temperature of 30 ° C. [η]. ] Is converted to the intrinsic viscosity (IV) of phenol / tetrachloroethane = 60/40 by the following formula.

 IV = 0.8325 x [η] + 0.005.

The intrinsic viscosity of the yarn containing the compound was measured by using a Soxhlet extractor, which was previously extracted with acetone for 3.0 hours, and further dried at 120 ° C. for 6 hours under reduced pressure.

<Measurement method of residual amount of added compound in yarn> Using a differential thermal balance TG-DTA high temperature type manufactured by Rigaku Denki Co., Ltd., a sample weight of 5 mg was heated in an argon gas stream to an atmosphere sample at a temperature starting temperature of 20 ° C., and the sample was heated. Temperature end temperature 500 ° C, sample heating rate 20 ° C
/ Min, and the amount of the added compound remaining in the sample was determined from the weight loss curve.

<Measurement method of glass transition temperature> Toyo Baldwin Co., Ltd., Rheo Viblon (Rheo Viblon)
ron) Using a DDV-II EA type dynamic viscoelasticity measuring device, the sample
The temperature (° C.) at which tan δ rises in dry air at mmg, a measurement frequency of 110 Hz, and a temperature rising rate of 1 ° C./min was determined, and the temperature was adopted as a measure of the glass transition temperature.

<Method of Measuring Fiber Fineness> The fineness was measured by a test method and conditions based on 7.3 of JIS L 1013 (1981).

<Measurement method of fiber strength> The tensile strength (strength) of the fiber is JIS L 1013 (1981) 7.5.
In accordance with 1), in a standard condition laboratory, a constant-speed elongation type universal tensile tester Tensilon UTM manufactured by Toyo Baldwin Co., Ltd.
-III was used to measure the tensile strength of the single fiber.

However, the measurement conditions were 5 kgf, using a tension type load cell, gripping interval 10 cm, pulling speed 10 cm / min, recording paper feed speed 100
The sample was pulled at a rate of cm / min, and the load (g) when the sample was cut was used to calculate the tensile strength (g / d) according to the following formula.
/ d).

Tensile strength (g / d) = strength at cutting (g) / fineness of sample (d) <Method of measuring initial tensile modulus of fiber> The initial tensile resistance (initial tensile modulus) of the fiber is as described above. JI
The test was performed in the same manner as the fiber strength test method according to 7.5.1 of SL 1013 (1981), and a one-elongation curve of the load was drawn on the recording paper. Initial tensile resistance (g / d) by initial tensile resistance calculation formula
Was calculated as the initial tensile modulus (g / d).

<Measurement method of birefringence (Δn)> Using a Nikon polarization microscope POH type and a Rights Berek concentrator, the retardation (Γ) of the fiber is measured from the interference fringe and the extinction angle, and the fiber diameter is measured using a micrometer. (D) Measured and birefringence index (Δn) according to the following equation
I asked. As a light source, a starter for a spectral light source (Toshiba SLS-8-B type Na light source) was used.

Δn = Γ / D (Γ: retardation) (Action) The fact that the ethylene terephthalate-based polyester fiber obtained in the present invention has excellent physical properties such as high strength and high elastic modulus is a specific compound which is compatible with the polymer. Is added to the polymer in a specific ratio to reduce the melt viscosity and enable practical molding, and at the same time, in drawing the obtained undrawn yarn, the compound is cooled and solidified when the polymer is cooled. The present inventors speculate that it plays a role of a plasticizer to reduce the number of entanglements of the molecular chains, and enables the polyester molecular chains to be highly stretched.

(Examples) Next, the characteristics of the present invention will be described in detail with reference to examples.

Example 1 As a catalyst, antimony trioxide (for terephthalic acid,
A polyethylene terephthalate chip (intrinsic viscosity: 0.6) containing 0.05 mol% of antimony) was blown with nitrogen gas in a heat medium of triphenyl hydride while blowing nitrogen gas.
℃, heat and stir for 20 hours, heat medium polymerization is carried out, limiting viscosity
2.0 polyethylene terephthalate was obtained. The polyester chip was dried under reduced pressure at a temperature of 120 ° C. for 16 hours, and then 200 parts by weight of 1-methylnaphthalene (distilled product, manufactured by Nippon Steel Chemical Co., Ltd.) was added to 800 parts by weight of the polymer. The temperature was raised to 0 ° C., and the mixture was stirred under a reduced pressure of 1.0 mmg for 2 hours. After the stirring for a predetermined time was completed, the polymer was taken out of the mixing and stirring vessel, but no 1-methylnaphthalene remained in the vessel. Also, no adhesion of 1-methylnaphthalene was observed on the surface of the treated polyester chip. By performing such processing, 1
-Polyethylene terephthalate impregnated with -methylnaphthalene was obtained. A change in weight of the polyester chip due to heating was measured by a thermobalance device, and a weight reduction of 19.8% was shown. In addition, the weight reduction of the polyethylene terephthalate chip to which 1-methylnaphthalene was not added was measured in the same temperature range using the above measuring apparatus, and the weight loss was 0.2%.
The above polyethylene terephthalate chip to which 1-methylnaphthalene is added is melted at a polymer melting temperature of 270 ° C. using an extruder-type small spinning machine, and the pore diameter is φ0.28 mm.
Melting and discharging were performed at a spinneret temperature of 310 ° C from the spinneret having 24 holes and a discharge rate of 0.31 g / min per single hole of the spinneret.
After cooling and solidifying by blowing an air current at a speed of 3 m / sec, about 0.5% of an oil agent is applied to the yarn, and the take-up speed is 15.2%.
It was changed in the range of ~ 250m / min and wound up. The zero shear viscosity of the polyester at the spinneret temperature was 13,600.
Poise. The birefringence (Δn) of the undrawn yarn wound at a take-up speed of 100 m / min was 0.0002, and the natural stretching ratio at a temperature of 22 ° C. was 3.78. The amount of 1-methylnaphthalene remaining in the undrawn yarn was 12.6% by weight.
And the glass transition temperature determined from the dynamic viscoelasticity measurement is 4
4.5 ° C. Then, the undrawn yarn was heated to a temperature of 60 ° C. between a supply roll and a first draw roll having a surface speed of 50 m / min. After stretching in the first stage, the film is further stretched with a second stretching roll through a non-contact type hot plate heater heated to a temperature of 245 ° C. at a second stretching ratio shown in Table 1 and a winder. Rolled up. The performance of the obtained drawn fiber is as shown in Table 1. Birefringence of undrawn yarn is 0.00
Except when the value was less than 01 (Comparative Example No. 1) or when the birefringence exceeded 0.02 (No. 2), etc., each had a high tensile speed and an initial tensile elastic modulus, except for the cases.

Example 2 A polyethylene terephthalate polymer having intrinsic viscosities of 0.9, 1.3, 3.0, and 3.5, respectively, was obtained by adjusting the polymerization time of the heat medium in Example 1. Each polymer was mixed and impregnated with 1-methylnaphthalene using the apparatus and conditions described in Example 1. The polymer was melt-discharged using the spinning apparatus described in Example 1. Naturally, the pressure applied to the spinneret during melt extrusion and the characteristics of the spun yarn vary greatly depending on the intrinsic viscosity of the polyester polymer used for spinning. Regarding the discharge amount per single hole, etc., the spinning conditions were optimized for each polyester polymer having a different intrinsic viscosity. The obtained undrawn yarn was drawn by the method described in Table 2. Other conditions were the same as in Example 1.
The results are shown in Table 2. As is clear from Table 2, those belonging to the present invention (Nos. 2 to 3) can be melt-extruded with a relatively low melt viscosity, and the fibers obtained by drawing have extremely high strength and initial elastic modulus. It turns out that it is high. On the other hand, when the polyester polymer having the intrinsic viscosity of 0.9 was used (No. 1), the effect of improving the strength and the initial elastic modulus of the drawn yarn was small. When a polyester polymer having an intrinsic viscosity exceeding 3.0 (No. 4) was used, the melt viscosity was 53,200 poise, and the spinning state was extremely unstable, so that a homogeneous undrawn yarn could not be obtained.

Example 3 Mixing and impregnating treatments were performed under the method and conditions described in Example 1 by changing the mixing ratio of 1-methylnaphthalene to 1,000 parts by weight of the raw material polyester in the range of 0 to 1250 parts by weight. The mixture was spun using the spinning apparatus described in Example 1, respectively.
Stretching was performed by the method. Table 3 shows the results. As is clear from Table 3, those belonging to the present invention (Nos. 3 to 6) had a discharge pressure at the time of practical use at the time of melt spinning, and the spinning state was stable. The yarn obtained by drawing each undrawn yarn showed high values in both strength and initial elastic modulus. On the other hand, when 1-methylnaphthalene is not added (N
o.1) has extremely high back pressure at the spinneret during melt discharge,
Spinning was not possible. In the case of No. 2 which does not belong to the present invention,
Although spinning was possible, the resulting undrawn yarn had extremely large yarn spots both between single fibers and in the longitudinal direction of the yarn, so that drawing at a high magnification was impossible. In addition, in the case of No. 7 which does not belong to the present invention, when an extruder type spinning device was used, leakage of the compound from the barrel portion occurred, and furthermore, a large amount of 1-methylnaphthalene gas from the discharge yarn immediately below the spinneret was used. Smoke was observed.

Example 4 Example 1 was applied to the polyester polymer described in Example 1.
Based on the apparatus and conditions described in the above, biphenyl, diphenylyl ether, monoethyl biphenyl, which is compatible with the polymer at a temperature of 210 ° C. or more, and 210 ° C.
At the above temperature, the hydrogenated terphenyl incompatible with the polymer was independently mixed and impregnated. Naturally, the mixing temperature and time were adjusted in accordance with the type of compound used. Based on the spinning and drawing conditions described in Example 1, the polyester chips after the mixing treatment were used to prepare drawn yarns while slightly modifying the conditions according to the type of compound used. The results are shown in Table 4. As is clear from Table 4, those belonging to the present invention (No.
In the case of 3), the melt viscosity in spinning was at a level that could be dealt with in terms of equipment, and the obtained drawn yarn showed high values in strength and initial elastic modulus. On the other hand, in the case of No. 4 which does not belong to the present invention, the spinning state, particularly the supply of the raw material polymer to the spinning machine was unstable, and continuous stable operation was difficult.
The obtained undrawn yarn had extremely low drawability, and the desired high-performance fiber could not be obtained.

Example 5 100 parts by weight of 1-methylnaphthalene and 100 parts by weight of diphenyl ether were added to 800 parts by weight of the polyester polymer described in Example 1 and mixed and impregnated with the apparatus and conditions described in Example 1. Was performed. The polyester containing the mixed compound was spun and stretched by the apparatus and conditions described in Example 1. Table 5 shows the results. The obtained drawn yarn exhibited high strength and initial tensile modulus.

(Effects of the Invention) According to the present invention, the spinning speed of a high-molecular-weight ethylene terephthalate-based polyester, which has been particularly difficult to achieve a high strength and a high initial elastic modulus by a conventionally known spinning and drawing method because the melt viscosity is too high, is 50 m / High speed productivity in more than a minute and stable spinning and drawing have become possible. That is, by adding a specific compound having compatibility with polyester at high temperature, the melt viscosity was reduced to a practical level, and thus stable spinning by existing spinning and drawing equipment became possible. In addition, conventionally, melt spinning at a low temperature, which could not be considered with ethylene terephthalate-based polyester, is possible,
As a result, a decrease in the intrinsic viscosity that occurs during the fiberization process can be suppressed. Furthermore, the above-mentioned undrawn yarn has high drawability, and since it can be drawn at a high magnification, it is possible to stably obtain a polyester fiber excellent in both strength and initial elastic modulus, contributing to the industry. It is.

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Shuji Chiba 2-1-1 Katata, Otsu City, Shiga Prefecture Examiner, Toyo Spinning Co., Ltd. General Research Laboratory Shigeki Takagi (56) References JP-A-2-216218 (JP, A) JP-A-1-162820 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) D01F 6/92, 6/62 F term theme code 4L036

Claims (1)

(57) [Claims] An ethylene terephthalate-based polyester having an intrinsic viscosity (IV) of 1.0 to 3.0 is mixed with a compound compatible with the ethylene terephthalate-based polyester at a temperature of 210 ° C. or more with respect to the ethylene terephthalate-based polyester.
50% by weight, melted and extruded from the nozzle orifice, then cooled and solidified and taken out of the spun yarn, stretched continuously or once after spinning, and then stretched. Method for producing high-density polyester fiber.