JP2882697B2 - Polyester fiber and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyester fiber having an extremely thermally stable internal structure. More specifically, the present invention relates to a polyester fiber having a high modulus of elasticity, high fatigue resistance, and having a significantly improved thermal dimensional stability, which is particularly suitable as a reinforcing fiber for a rubber structure, and a method for producing the same.

[0002]

2. Description of the Related Art Polyester fibers, especially polyethylene terephthalate fibers, have high strength and initial elastic modulus and are excellent in various characteristics such as dimensional stability and durability. Therefore, they are used to reinforce rubber structures such as V-belts, conveyor belts and tires. Widely used as fiber for textiles. In particular, in the case of automobile tires, the use amount of polyester fibers has been increasing in recent years because such characteristics of polyester fibers match the required performance as a radial tire carcass material for passenger cars.

[0003] However, when looking at the performance of each of the rubber reinforcing fibers, there remains a problem that thermal dimensional stability relating to heat shrinkage is inferior to rayon and fatigue resistance is lower than that of polyamide fibers. There was a need for improvement.

[0004] In particular, if the thermal dimensional stability of polyester fiber is improved to the same level as rayon fiber, so-called "post cure-inflation", which is a "correction of tire distortion" step in tire molding, can be omitted. It is expected that its position will be further increased in the future as a rubber reinforcing fiber that is more cost-effective than fiber.

In order to obtain polyester fibers having improved thermal dimensional stability and fatigue resistance, for example, JP-A-53-58031, JP-A-57-154410, and JP-A-5-154410
No. 7-161119, Japanese Patent Application Laid-Open No. 58-98419, etc., use a polyester having a high degree of polymerization and perform high stress spinning to obtain a relatively highly oriented undrawn yarn (so-called PO).
Y) and a method of stretching the same are known (hereinafter, referred to as “Y”).
"POY-stretching method").

[0006] However, the polyester fiber obtained by the above-mentioned "POY-drawing method" can certainly improve the thermal dimensional stability and fatigue resistance, but when it is used as a substitute for rayon fiber. The above thermal dimensional properties are still inferior to rayon fibers, and other properties required as rubber reinforcing fibers, such as melting point,
It cannot be said that the thermal stability at the time of raising the temperature, such as strength and work loss, could not be sufficiently improved.

On the other hand, JP-A-61-41320, JP-A-62-69819, JP-A-63-159518, and
As disclosed in 63-165547, etc., the stress during spinning is further increased to obtain a more oriented undrawn yarn and stretched it (hereinafter referred to as “a method for stretching a highly oriented undrawn yarn”. Name.)
Accordingly, a method of producing a polyester fiber having a thermal dimensional characteristic closer to rayon has been proposed. However, it cannot be said that the high-polymerization degree polyester is made to have higher stress by increasing the spinning speed, and the obtained highly oriented undrawn yarn is drawn, which does not fall within the technical range of the above-mentioned proposal.

That is, in the conventional “POY-drawing method” or “drawing method of a highly oriented undrawn yarn”, a high degree of polymerization polyester is spun at a high speed in order to obtain a highly oriented multifilament undrawn yarn. In addition, the obtained polyester fiber does not sufficiently satisfy the thermal dimensional stability and the properties at the time of temperature rise. Furthermore, when a high-polymerized polyester and a multifilament extrudate are spun at such a high speed, insufficient cooling between the multifilament single yarns and an increase in the accompanying flow during spinning occur, resulting in the fusion of the single yarns. In addition, yarn twisting occurs, causing a problem that the uniformity between single fibers becomes extremely poor as the number of yarn breaks and fluff increases.

[0009] This leads to deterioration of the stretchability to be performed subsequently, and the strength and strength of the obtained polyester fiber.
It has a drawback that the processing performance such as elongation and twisting / adhesion treatment is also reduced. In addition, due to the above-mentioned deterioration of spinnability, it is not possible to achieve a sufficiently high orientation of the multifilament undrawn yarn, and as a result, a dramatic improvement in thermal dimensional characteristics and characteristics during temperature rise is achieved. Is a difficult situation.

Hereinafter, the prior art will be described in more detail. First, Japanese Patent Application Laid-Open No. 58-58031 discloses a high-strength polyester fiber having a low hysteresis characteristic. Specifically, a polyester chip having a relatively high intrinsic viscosity is used, the spinning speed is suppressed, and high strength is achieved at a high draw ratio. However, the strength TS ratio to the intrinsic viscosity [η] of the polyester fiber is not always sufficient, and the stability coefficient calculated from the work loss ΔE and the dry heat shrinkage rate HS is 6 to 45. The fatigue resistance is not sufficient. Next, JP-A-63-
Japanese Patent No. 159518 discloses that, using a polyester chip having a relatively high intrinsic viscosity, ultra-high-speed spinning is performed and then hot drawing is performed, so that the elongation E1 at the secondary yield point is reduced from the secondary yield point to the cutting point. The ratio of elongation E2, ie E2 / E
Polyester fibers with improved fatigue properties by increasing the value of 1 are disclosed. However, TS / [η] decreases,
When E2 / E1 is increased, there is a problem that the strength decreases due to a decrease in chemical stability when the fiber is used as a reinforcing fiber for a rubber structure. JP-A-57-154410 discloses a polyester fiber having a low terminal modulus by subjecting an undrawn yarn obtained at a spinning speed of 2.0 to 5.5 km / min to a high drawing ratio by hot drawing. . Since this fiber has a high dry heat shrinkage HS, the stability coefficient calculated from the work loss ΔE and the dry heat shrinkage HS is extremely small, and the fiber has poor thermal dimensional stability and fatigue resistance.

[0011]

SUMMARY OF THE INVENTION In view of the above, the inventor of the present invention has determined that the excellent thermal characteristics at the time of temperature increase, which do not impair the excellent properties of high elastic modulus and high fatigue resistance, are comparable to rayon fibers. The present invention has been accomplished by industrially stably supplying polyester fibers having thermal dimensional stability at the same time.

That is, an object of the present invention is to provide a polyester fiber for reinforcing a rubber structure, and more particularly, to use a polyester having a relatively low degree of polymerization to have a high modulus of elasticity and high fatigue resistance, as well as a melting point, strength and work loss. The present invention provides a polyester fiber which is extremely stable at the time of temperature rise and has remarkably improved thermal dimensional stability such as heat shrinkage and heat shrinkage stress.

[0013]

The polyester fiber of the present invention is a polyester fiber having ethylene terephthalate as a main repeating unit and has the following properties (a) intrinsic viscosity [η] = 0.50 to 0.75 ( b) Peak value of mechanical loss tangent (tan δ) and peak temperature (Tmax) tan δ ≦ 0.140 Tmax ≦ 130 ° C. (c) Elongation at secondary yield point relative to elongation E1 from secondary yield point to break point E2 / E1 = 0.20 to 0.49 (d) Work loss ΔE at 150 ° C. and dry heat shrinkage HS at 175 ° C.
(However, the stability coefficient represented by the reciprocal of the product of 2.2% or less) is 50 or more. (E) Ratio of strength TS to intrinsic viscosity [η] TS / [η] ≧ 9.2 (However, the above ( The definition of the properties a) to (e) will be described in detail in the specification text).

The polyester fiber of the present invention is preferably produced by a production method having the following features. That is, in producing a polyester fiber having an ethiten terephthalate unit as a main repeating unit. Melt spinning a polyester having an intrinsic viscosity of 0.50 to 0.80 at a spinning speed of at least 6.0 km / min; In hot stretching the undrawn yarn, a draw ratio DR
And keeping the hot stretching temperature DT so as to satisfy the following (1) to (3), DR = 1.20 to 1.30 (1) (Tg-10) ≦ DT ₁ ≦ (Tg + 100) (( 2) (Tg + 100) ≦ DT ₂ ≦ Tm ₂ (3) (However, DT ₁ is the stretching temperature in the early stage of stretching, and DT ₂ is the stretching temperature in the latter stage of stretching.) C. After the above stretching, a relaxing heat treatment is performed (however,
Above a. ~ C. The definition of the property of is described in detail in the text of the specification. ), Which is a method for producing a polyester fiber.

Next, the characteristics of the polyester fiber of the present invention will be described in detail. First, the intrinsic viscosity [η] of the polyester fiber of the present invention needs to be 0.50 to 0.75. If the intrinsic viscosity [η] is less than 0.45, the strength of the polyester fiber cannot be sufficiently increased, and is not suitable as the intended rubber structure reinforcing fiber.

Further, if melt spinning is performed at a high spinning speed of 6.0 (km / min) or more to obtain a polyester fiber having an intrinsic viscosity [η] of more than 0.75, insufficient cooling between multifilament single fibers may occur. The accompanying flow of the spinning increases, and the fusion of the single yarn and the twisting of the yarn occur, and the uniformity between the single fibers becomes extremely poor with the increase of the yarn breakage and the fluff.
As a result, the multifilament undrawn yarn is not given a sufficiently high orientation, resulting in a dramatic improvement in thermal characteristics and thermal dimensional characteristics comparable to our target rayon fiber. Can not do it. Therefore, the present invention
It is characterized by using a polyester having a low degree of polymerization to improve high strength and thermal dimensional stability.

Further, the deterioration of the spinnability leads to the deterioration of the subsequent drawing step, and the drawback that the processing performance such as the strength and elongation and the twisting / adhesion treatment of the obtained polyester fiber is reduced becomes apparent. Come.

The peak value tan δ of the mechanical loss tangent of the polyester fiber of the present invention is 0.14 or less, and the peak temperature
Tmax shows a very characteristic value of 130 ° C. or less. This will be described in detail with reference to the accompanying drawings. FIG. 1 shows the relationship between the peak value tan δ of the mechanical loss tangent and the peak temperature Tmax. In the figure, A is the tan δ-Tmax of the polyester fiber of the present invention, and B is the conventional “POY”.
Tanδ-Tm of polyester fiber obtained by “drawing method”
ax.

The polyester fiber according to the present invention has a “PO
Tanδ- compared to polyester fiber by "Y-drawing method"
It is clear that both values of Tmax are greatly reduced. Here, when Tmax is 130 ° C. or lower, the relaxation of the amorphous portion is remarkably relaxed due to the fine structure of the fiber, and the tan δ is 0.1 mm.
A value of 140 or less indicates that the stretching orientation is substantially sufficiently advanced. This indicates that the polyester fiber of the present invention has a sufficiently improved strength and elastic modulus, and is significantly improved in terms of fatigue resistance and thermal dimensional stability as compared with the polyester fiber of the “POY-drawing method”. Indicates that

Further, the polyester fiber of the present invention has a stress-
In the elongation curve, (1) the stress T1 at the secondary yield point is 5 g / d or more (2) the elongation E1 at the secondary yield point is 6 to 13% (3) the elongation E1 at the secondary yield point The elongation ratio E2 / E1 of the elongation E2 from the secondary yield point to the cutting point with respect to
It has the characteristic of 0.49 at the same time, and the elongation ratio E2 / E1 of the elongation E2 from the secondary yield point to the cutting point with respect to the elongation E1 at the secondary yield point is extremely characteristic. This elongation ratio E
2 / E1 is obtained at a stretching ratio of 1.20 to 1.30. When the stretching ratio is too small, it becomes 0.50 or more, and when it is too large, it becomes less than 0.20.

This will be described in detail with reference to the drawings. FIG. 2 shows a stress-elongation curve of the polyester fiber, in which curve a is the stress-elongation curve of the present invention, and curve b is the polyester fiber obtained by the conventional "POY-drawing method". 5 is a stress-elongation curve of the present invention. Here, the secondary yield point is a characteristic represented by the point (A) in the stress-elongation curve of FIG. 2, and the intersection of the curved tangents before and after the yield point is represented by θ / A straight line is drawn at an angle of 2 and determined by the intersection of this straight line and the stress-elongation curve.

In the case of a polyester fiber having an elongation ratio E2 / E1 of 0.50 or more, for example, when the fiber is used as a reinforcing fiber for a rubber structure, the rate of decrease in strength with respect to the original yarn becomes large. When the so-called vulcanization is carried out under the above condition, the strength reduction rate also increases, and it becomes impossible to exhibit sufficient toughness performance as a rubber structure reinforcing fiber. This fact is considered to be a phenomenon related to the internal microstructure of the fiber, and is one of the important points of the present invention. That is, 2
In the case of polyester fibers having a large elongation ratio E2 / E1 before and after the next yield point, the orientation as a fiber average, that is, the properties such as average birefringence and amorphous orientation are low, and particularly, the adhesive and rubber structure It is considered that the chemical stability against moisture or amines in the product deteriorates.

In the case of a polyester fiber having an elongation ratio E2 / E1 of less than 0.20, the resulting fiber is excessively stretched and oriented, and the reduction in the strength utilization factor with respect to the original yarn in the case of a twisted cord increases. It is not preferable. The elongation ratio E2 / E1 at the secondary yield point is preferably 0.20 to 0.47.

The stress T1 at the secondary yield point is 5.0 g / d
The lower polyester fiber is not sufficiently twisted when it is twisted and then twisted, and then the adhesive is applied under high temperature and tension conditions to make the rubber structure reinforcing fiber. It is not suitable for intended reinforcement. Therefore, 2
The stress T ₁ at the secondary yield point preferably has a stress at the secondary yield point of 5.5 g / d or more.

On the other hand, polyester fibers having an excessively high elongation E1 at the secondary yield point result in insufficient drawing, resulting in low orientation as an average fiber. As a result, the chemical stability against moisture or amines deteriorates, and the utilization rate during adhesive treatment and rubber vulcanization decreases, and sufficient toughness performance as a reinforcing fiber for rubber structure cannot be exhibited. . Therefore, the elongation E ₁ at the secondary yield point is 13% or less, more preferably 6 to 10%.
It is. The elongation at break (E1 + E2) is 19.8%
It is as follows.

The polyester fiber of the present invention has a stability coefficient represented by the reciprocal of the product of the work loss ΔE at 150 ° C. and the dry heat shrinkage at 175 ° C. of 50 or more, more preferably 55 or more.
The work loss referred to here is a yarn length of 10 inches and a strain rate of 0.5
0.6g / d and 0.05g under the condition of inch / min and temperature 150 ℃
/ D is the hysteresis loss per 1000 denier obtained by measuring the hysteresis loop with a stress between / d and the unit of inch-pound. The lower the value is, the smaller the heat generated by repeated elongation and relaxation is. It is a parameter that plays an important role in improving the fatigue resistance of the fiber.

This will be described in detail with reference to the accompanying drawings. FIG. 3 shows the relationship between the dry heat shrinkage HS at 175 ° C. and the stability coefficient defined above. D in the figure indicates the range of the shrinkage factor-stability coefficient of the polyester fiber according to the present invention, and F indicates the range of the shrinkage factor-stability coefficient of the polyester fiber obtained by the above-mentioned "POY-drawing method". I have.

As apparent from the comparison between D and F, the characteristic of the polyester fiber of the present invention is that the dry heat shrinkage ratio and the work loss are both achieved at the same time. This is because a polyester fiber having a stability coefficient of 50 or more as well as extremely stable in elongation and relaxation changes as well as in a thermal change is obtained. On the other hand, the stability coefficient according to the prior art is only 20 at most, and while maintaining the spinning and drawing steps stably, high strength, high elastic modulus and the above stability coefficient value of 20
As described above, the fact that setting the value to 45 or more involves a very great difficulty is what the prior art (for example, JP-A-53-58031) teaches.

The stability factor of 50 or more is an essential requirement for obtaining the polyester fiber intended for the present invention, which has high fatigue resistance and significantly improved thermal dimensional stability comparable to rayon fiber. This feature is a low-viscosity polymer that is spun at high speed and can be obtained with a further limited draw ratio.
In the conventional “POY-drawing method” or “drawing method of highly oriented undrawn yarn”, the stability coefficient is 50 or less, and any of the thermal dimensional stability and fatigue resistance is a weak point. Here, the work loss ΔE is 0.015 or less, preferably 0.010 or less. The dry heat shrinkage HS (175 ° C) at 175 ° C is
2.2% or less.

Further, the polyester fiber of the present invention has the following properties in addition to the above. The single fiber cross ratio Cd of the polyester fiber of the present invention is 1.20 or less, and the uniformity between single yarns is remarkably improved as compared with the polyester fiber obtained by the conventional “POY-drawing method”. The single fiber cross ratio is a value obtained by dividing the maximum diameter of all the multifilaments by the minimum diameter, and is an important parameter that is a measure of the uniformity between the single fibers. Single fiber cloth ratio Cd
Is preferably 1.15, more preferably 1.10 or less.

The preferred cross ratio of the present invention is such that the intrinsic viscosity [η] is more efficiently obtained in the range of 0.50 to 0.75. The ratio of the strength TS to the intrinsic viscosity [η] of the polyester fiber of the present invention, that is, TS
/ [Η] is 9.2 or more, more preferably 9.5 or more. Conventionally, it is common knowledge for those skilled in the art that the intrinsic viscosity is 0.90 or more in order to improve the strength of polyester fibers. However, in the conventional “POY-drawing method” and “drawing method of highly oriented undrawn yarn”, even if a polyester fiber having an intrinsic viscosity of 0.90 or more is obtained,
[Η] does not become 9.2 or more, and it is a big problem to sufficiently develop its strength. This is due to the fact that those skilled in the art generally understand that a highly oriented unstretched yarn, in other words, an unstretched yarn having a higher birefringence has generally poorer stretchability. However, surprisingly, despite the fact that the polyester fibers according to the invention are obtained by drawing undrawn yarns having a very high orientation, their strength ratio is very high, preferably 9.2 or more, preferably 9.5 or more. Has a high value.

As described above, the improvement in the strength ratio with respect to the intrinsic viscosity is due to the fact that the polyester fiber of the present invention is a polyester multifilament having an extremely good single fiber cross ratio and excellent uniformity. This can be explained by the fact that the stretching is performed very uniformly. The product of the crystal melting point Tm2 and the density ρ of the polyester fiber of the present invention is
It is at least 370, more preferably at least 375, and is characterized by extremely high crystallinity.

Here, the crystal melting point Tm2 is 268 ° C. or higher, preferably 269 ° C. or higher, and the density ρ is 1.398 or higher, preferably 1.400 or higher. The melting onset temperature Tm1 measured from the melting curve of the DSC is 260 ° C. or higher, preferably 265 ° C.
It is. On the other hand, the conventional "POY-stretching method"
The product of the crystal melting point Tm2 of the polyester fiber and the density ρ of the polyester fiber is only 369 even if it is very high, and the melting start temperature
Tm1 also stays at 253-258 ° C.

This will be further explained from the fine structure.
Crystallinity X calculated from density of 55% or more, and the crystal size D _c is equal to or is 50Å or more. This indicates that the polyester fiber of the present invention is substantially sufficiently stretched, and suggests that there is little decrease in mechanical properties such as strength and initial modulus when the temperature is increased, High-temperature steaming and high-temperature dry heat treatment (for example, 200 to 260 ° C) in the adhesive heat treatment and vulcanization treatment processes for reinforcing rubber structures, and the actual use temperature in rubber (for example, 100 to 200 ° C for tires and belts) It shows that it has high resistance.

Since the polyester fiber of the present invention has both high crystallinity and relaxation of the distortion of the amorphous portion as described above, it exhibits an unprecedented temperature-rising heat characteristic as shown below. Can be. The polyester fiber of the present invention,
Extremely high resistance to heat, temperature-dependent parameter ΔTS / of cutting strength in the temperature range from room temperature to 250 ° C.
T is 0.020 g / d / ° C or less, preferably 0.018 g / d /
° C or lower, more preferably 0.015 g / d / ° C or lower. The fact that the temperature-dependent parameter ΔTS / T of the cutting strength is low means that the rate of decrease in strength with respect to an external temperature rise is low, and particularly when the polyester fiber is used as a reinforcing fiber for a rubber structure, for example, in a tire. In other words, it shows high resistance to temperature rise during running. This will be described in more detail with reference to the accompanying drawings. FIG. 4 shows the change in strength of the polyester fiber when heated, G in the figure shows the change in strength of the polyester fiber according to the present invention when heated, and H indicates the above-mentioned “POY-drawing method”.
Is the strength change during heating of the polyester fiber obtained by the method. As is clear from the comparison between G and H in this figure, the polyester fiber of the present invention has a very low temperature dependency on strength, and the temperature-dependent parameter ΔTS / T of the cutting strength is low.
It is characterized by being at most 0.020 g / d / ° C.

The polyester fiber of the present invention is characterized in that a shrinkage rate temperature-dependent parameter ΔHS / T, which is indicated by a change in dry heat shrinkage when the temperature is raised, is 0.040% / ° C. or less.

This will be described in more detail with reference to the accompanying drawings. FIG. 5 shows the dry heat shrinkage of the polyester fiber at various temperatures. In the figure, I shows the relationship between the temperature and the shrinkage of the polyester fiber according to the present invention, and J shows the relationship between the temperature and the shrinkage of the polyester fiber obtained by the above-mentioned "POY-drawing method". As is clear from the comparison between I and J in the figure, the polyester fiber of the present invention is characterized by a low dry heat shrinkage and an extremely low change in shrinkage due to heating temperature. The low shrinkage temperature-dependent parameter ΔHS / T indicates that the change in thermal dimensional stability with respect to an external temperature is small, which indicates that the polyester fiber is workable when reinforcing the rubber structure. Is uniform and stable. For example, it means that a change in strain during vulcanization is small.

Shrinkage temperature-dependent parameter ΔHS / T
Is preferably 0.025% / ° C. or less, more preferably 0.025% / ° C. or less.
17% / ° C or less. Further, the polyester fiber of the present invention shows substantially no shrinkage stress up to 200 ° C. in the heat shrinkage stress curve and 0.10 g / g at 255 ° C. or more.
d) It is characterized by having the following heat shrinkage stress peak.

The heat shrinkage stress has an extremely important meaning in determining the thermal dimensional stability of the fiber together with the heat shrinkage. That is, if the heat shrinkage or the heat shrinkage stress is large, for example, when the fiber is used as a reinforcing fiber in a rubber tire, if it is left as it is after vulcanization, it is deformed due to the heat shrinkage stress, and the size is reduced. ,
The problem of non-uniformity arises. Therefore, an extra step called so-called post-cure inflation, which waits for cooling while applying pressure from the inside so that the tire after vulcanization does not shrink, is required.

As described above, the polyester fiber of the present invention has a significantly smaller heat shrinkage than the conventional one,
Further, the present invention has also achieved an unprecedented improvement in heat shrinkage stress. This will be described in detail with reference to the accompanying drawings. FIG. 6 shows a temperature-heat shrinkage stress curve obtained by plotting the heat shrinkage stress at each temperature. In the figure, c shows the temperature-heat shrinkage stress curve of the polyester fiber according to the present invention, and d shows the temperature-heat shrinkage stress curve of the polyester fiber obtained by the conventional "POY-drawing method".

As apparent from the comparison between c and d, the polyester fiber c of the present invention shows no substantial increase in shrinkage stress up to 200 ° C. in the temperature-heat shrinkage stress curve, and It is characterized by having a thermal stress peak of not more than 0.10 (g / d) at 255 ° C. or more. On the other hand, the temperature-heat shrinkage stress curve d of the polyester fiber obtained by the conventional “POY-drawing method” shows that the heat shrinkage stress already starts to increase at around 100 ° C. Has increased sharply, and 0.17 (g /
d) It is clearly distinguished from the polyester fiber of the present invention by having the following peaks.

The polyester fiber of the present invention has a heat shrinkage stress up to 200 ° C. of 0.02 (g / d) in a heat shrinkage stress curve.
Or less, preferably 0.015 (g / d) or less,
No substantial increase in heat shrinkage stress is exhibited.

Next, a method for producing a polyester fiber according to the present invention will be described. The polyester fiber according to the present invention has an intrinsic viscosity of 0.50 to 0.80, melts and discharges a raw material polyester chip having ethylene terephthalate as a main repeating unit, and spins at a spinning speed of 6.0 km / min or more. It is suitably obtained by hot stretching. In general, it is known that in melt spinning of polyester, ester bonds are cleaved by thermal decomposition or hydrolysis, and the molecular weight is reduced. As a result, [η], which is an index of the molecular weight, also decreases. Therefore, in order to obtain a polyester fiber having an intrinsic viscosity [η] of 0.50 to 0.75 in the present invention, an intrinsic viscosity [η] of 0.5 to 0.75 is required.
It is preferable to use a polyester chip of 0 to 0.80 as a raw material. In the present invention, the polyester is such that 85 mol% or more of its repeating units are composed of ethylene terephthalate units, and is particularly intended for polyethylene terephthalate produced from terephthalic acid or a functional derivative thereof and ethylene glycol.

However, terephthalic acid, which is an acid component constituting polyethylene terephthalate, or a part of its functional derivative is less than 15 mol%, for example, isophthalic acid, adipic acid, sebacic acid, azelaic acid, naphthalic acid,
A bifunctional acid such as p-oxybenzoic acid or 2,5-dimethyl terephthalic acid, or at least one of functional derivatives thereof, is used, or a part of ethylene glycol which is a glycol component is 15 mol. % Of 2 such as dielene glycol, 1-4 butanediol, etc.
The copolymer may be replaced with at least one of the hydric alcohols. Further, these polyesters may contain an antioxidant, a flame retardant, an adhesion improver, a matting agent, a coloring agent, and the like.

The concentration of the terminal carboxyl group of the polyester used in the present invention is 30 (equivalents / 10 ⁶ g) or less.
It is preferably 20 or less, more preferably 15, and if necessary, for example, an epoxy compound, a carbonate compound,
A terminal carboxyl group blocking agent such as a carbodiimide compound is added and mixed in a spinning extruder. The obtained terminal carboxyl group concentration of the present invention is 25 (equivalent / 10 ⁶ g) or less, preferably 15 or less, more preferably 10 or less.

The polyester fiber of the present invention can be obtained by melt-spinning a raw material polyester chip containing ethylene terephthalate as a main repeating unit using a conventional screw extruder. The polymer temperature at the time of extrusion is 310 ° C. or less. The hole diameter of the spinneret is 0.2-0.7
It is desirable that the arrangement of mm and holes is 1 to 5 annular rows.
The denier per filament is preferably 3 to 10 d / f.

The spun yarn discharged from the spinneret immediately has a length of 5 cm or more and an internal atmosphere temperature of 150 ° C. to 350 ° C.
Is passed through the heating zone. Next, it is cooled and solidified by passing the cooling air from the outer periphery through a cooling device. The above-mentioned extrusion and cooling conditions are extremely important for keeping the uniformity of the obtained polyester fiber, especially for keeping the single fiber cloth ratio low.

Next, the spun yarn that has been cooled and solidified is fed with a predetermined amount of oil agent using an oil supply nozzle as a convergence guide, and then a spinning speed of 6.0 (km / min) or more, preferably,
It is wound as an undrawn yarn at a spinning speed of 6.0 to 8.0 (km / min). By limiting the spinning speed in this way,
Since tan δ and Tmax of the present invention can be suppressed low and the stability coefficient can be increased, the thermal dimensional stability and fatigue resistance can be improved.

Next, the relationship between the characteristics of the undrawn yarn thus obtained and the polyester fiber of the present invention will be described in detail. The peak value tan δ of the mechanical loss tangent of the undrawn yarn for polyester fiber of the present invention is 0.165 or less, and its peak temperature Tmax is 120 ° C. or less.

As described above, the polyester fiber of the present invention is characterized in that tan δ is 0.140 or less and Tmax is 130 ° C. or less. In order to obtain this fiber, the undrawn yarn has a tan δ of 0.165 or less. In addition, it is necessary to keep Tmax at 120 ° C. or less. That is, the value of tanδ-Tmax of the fiber is
It is also changed by drawing and heat treatment, and the polyester fiber characteristic of the present invention can be obtained only by drawing / heat-treating the undrawn yarn having the above-mentioned microstructural characteristics as described below.

This will be described with reference to the accompanying drawings. FIG. 1C shows the tan δ-Tmax of the undrawn yarn according to the present invention, and it can be seen that the range of tan δ-Tmax is moved in the direction of the polyester fiber A of the present invention by the drawing and heat treatment.
The birefringence Δn of the undrawn yarn for polyester fiber of the present invention is:
The spinning speed V (km / min) is maintained so as to satisfy the following expression. ^{(0.058V-0.004V 2 -0.105) ≦} Δn ≦ (0.058V-0.004V 2 -0.059) undrawn yarn birefringence, as well count the degree of fiber orientation, the microstructure formed of a polyester fiber after drawing and heat treatment It is one of the important parameters that greatly affects the thermal dimensional stability and fatigue resistance.

The relationship between the spinning speed and the undrawn yarn will be described with reference to the accompanying drawings. In FIG. 7, K is the birefringence of the undrawn yarn of the present invention, and L is the birefringence of the undrawn yarn by the conventional “POY-drawing method”. The unstretched polyester yarn of the present invention indicates that the birefringence is substantially at a critical point in relation to the spinning speed, and thus the unstretched yarn highly oriented is used. And

The birefringence of the undrawn yarn of the present invention is 0.099 or more, preferably 0.110 or more, more preferably 0.120 or more. Further, the birefringence Δn _c of the crystal phase of the undrawn yarn for polyester fiber of the present invention is 0.190 or more, and the relationship with the crystallinity X _c (%) by wide-angle X-ray diffraction satisfies the following expression. It is characterized by being maintained in a similar manner. X _c ≧ (1337Δn _c −202) The crystal phase birefringence Δn _c indicates the orientation of the crystal part.
The undrawn yarn of the present invention has high crystallinity and high crystal orientation.

As described above, maintaining the crystal phase birefringence and the crystallinity simultaneously high means increasing the strength, density, and crystal melting point of the polyester fiber obtained by drawing and heat treatment. When it is used as a reinforcing fiber, it plays an important role in expressing toughness and elastic modulus and improving heat resistance. The crystal phase birefringence Δn _c is 0.190 or more, preferably 0.195 or more, and the crystallinity is 52% or more, preferably 60% or more, more preferably 65% or more.

Next, the stretching and heat treatment during the production of the polyester fiber according to the present invention will be described. First, the unstretched yarn or unstretched package cheese obtained under the above spinning conditions is stretched in one stage or in two or more stages. In the case of another stretching, the stretching winding speed is optional, but in consideration of stretching stability and productivity, 500 to 3000
A range of m / min is preferred.

In the above stretching, the stretching ratio DR and the stretching temperature DT are extremely important in determining basic physical properties such as toughness, elastic modulus, poor vulcanization and dimensional stability of the polyester fiber. First, the draw ratio DR can be determined by the following equation based on the birefringence Δn of the undrawn yarn. (2.00-12.3Δn + 43.6Δn ² ) ≦ DR ≦ (2.6-16.5 Δn + 50.0Δn ² ) It is generally recognized that there is a correlation between the birefringence of the undrawn yarn and the draw ratio. However, the relationship between the birefringence and the draw ratio of an undrawn yarn obtained by ultra-high-speed spinning at 6.0 km / min or more as in the present invention has not yet been clarified because of the drawability.

The present inventor further studied the draw ratio DR of the undrawn yarn having an extremely high birefringence, and as a result, the following formula (1) DR = 1.20 to 1.30 (...) By satisfying 1), it has been found that there are no fluff or yarn breakage, and that various properties such as toughness, elastic modulus, chemical resistance and thermal dimensional stability are efficiently exhibited. That is, in the method of the present invention for drawing an undrawn yarn obtained by ultra-high-speed spinning at 6.0 km / min or more, the draw ratio is 1.
The polyester fiber obtained in the range of 20 to 1.30 has an elongation ratio E ₂ / before and after the secondary yield point on the stress-elongation curve.
E ₁ is suitably maintained in the range of 0.20 to 0.49,
High toughness, high elastic modulus, chemical stability, thermal dimensional stability, etc. are also suitably achieved. However, if the stretching ratio is too large, the fluff or yarn breakage frequently occurs, and the twist yarn strength utilization rate and the thermal dimensional stability are undesirably reduced. On the other hand, if the ratio is less than 1.20, not only does the toughness decrease, but also the chemical stability decreases.

The stretching temperature is preferably in the range of the following formulas (2) and (3). However, DT1 in the formula (2) indicates the stretching temperature in the first half of the stretching, and DT2 in the formula (3) indicates the stretching temperature in the second half of the stretching. Tg indicates the glass transition point of the fiber,
Tm2 indicates the crystal melting point of the fiber. (Tg−10) ≦ DT1 ≦ (Tg + 100) (2) (Tg + 100) ≦ DT1 ≦ (Tm2) (3) The drawing temperature is important in determining the basic performance of the polyester fiber together with the above-mentioned drawing ratio. Needless to say.

The drawn yarn thus drawn is successively relaxed and heat-treated at a temperature of 180 to 260 ° C. under a limit of 0.9 to 1.0 times, preferably 0.95 to 1.0. Is preferred. By this relaxation / heat treatment, the stress and strain up to the entire process are alleviated uniformly, and the final crystallinity and orientation of the fiber are determined. The birefringence of the polyester fiber of the present invention obtained by stretching the unstretched by the above method is 0.150 to 0.180.

The polyester fiber of the present invention obtained as a result has good uniformity at the single fiber level, and has excellent properties of high elastic modulus and high fatigue resistance. The resulting fiber also has thermal dimensional stability.

[0061]

EXAMPLES The production method of the present invention and the obtained polyester fibers will be described in more detail with reference to the following examples.
In addition, the definition of the characteristics and the measuring method described in the above description and the examples are shown below.

(1) Stress-elongation curve JISL-1017-1983 using Shimadzu Autograph SS-100
The measurement was performed according to (7.5). In addition, about the measurement of the temperature dependence parameter of cutting strength, it measured by the usual method except maintaining a fiber in the heating furnace heated to the predetermined temperature.

(2) Intrinsic Viscosity (η) Orthochlorophenol was measured using an Ostwald viscometer.
Reduced viscosity η of a solution in which 1 g of sample is dissolved in 100 ml
_sp / C was measured in a thermostat at 35 ° C., and [η] was calculated by the following equation. η _sp /C=[η]+0.277 [η] ²

(3) Terminal Carboxyl Group (COOH) The method was based on POHL method (Anal. Chem. 26 1616 (1957)). (4) Dry heat shrinkage rate HS Conforms to JISL-1017-1983 (7.10.2). (5) 150 ° C work loss ΔE A hysteresis loop can be measured at a stress between 0.6 g / d and 0.05 g / d under the conditions of a yarn length of 10 inches, a strain rate of 0.5 inches / minute, and a temperature of 150 ° C. The hysteresis loss per 1000 deniers was expressed in inches-pounds. The detailed method was based on JP-A-53-58031.

(6) Heat Shrinkage Stress Using a thermal stress tester (THERMAL STRESS tester: manufactured by Kanebo Engineering), the measurement was carried out at an initial load of 0.01 g / d and a heating rate of 100 ° C./min. (7) Birefringence Δn Using a polarizing optical microscope manufactured by Olympus, the birefringence was measured by a retardation method using a Bellec compensator using Na-D line as a light source and α-bromonaphthalene / olive oil as an immersion liquid.

(8) Single Fiber Cross Ratio Cd The single fiber diameter of all the filaments was measured from a micrograph of a cross-sectional photograph, and expressed as a ratio between the maximum diameter and the minimum diameter. (9) Dynamic loss tangent tan δ and peak temperature Tmax Toyo Baldwin Co., Ltd. Rheovibron DD
Using a V-II type dynamic viscoelasticity measuring apparatus, tan δ at each temperature was measured under the conditions of 0.1 mg of sample, measurement frequency of 110 HZ, and heating rate of 5 ° C./min. Here, for convenience, the peak value of the mechanical loss tangent was defined as tan δ, and the temperature at that time was defined as Tmax.

(10) Density ρ Measured at 25 ° C. using a density gradient tube adjusted from carbon tetrachloride / n-heptane. (11) Crystal melting point Tm2 and melting onset temperature Tm1 Using DSC-4 type manufactured by Perkin Elmer, heating rate was 20 ° C /
And the sample was measured at 4.0 mg, and the main peak temperature of the melting curve was determined by Tm.
And 2. The temperature at the intersection of the tangent line on the melting start side on the melting peak curve and the extension line of the baseline is defined as the melting start temperature.
Tm1.

(12) Crystallinity X by Density Method X was determined by the following equation from the measured density. X = {ρ _c (ρ−ρ _a ) / ρ (ρ _c −ρ _a )} × 100 where ρ: measured density ρ _c : 1.455 g / cm ³ ρ _a : 1.335 g / cm ³

(13) Crystal size D _{c Using a} X-ray generator (RU-200PL) manufactured by Rigaku Denki Co., Ltd., a monochromatic Cu-Kα ray (wavelength λ1.5418 °) with a nickel filter.
Was measured as a light source. Equatorial scan (0
The mean value was calculated from the half width of the 10) and (100) intensity distribution curves using Scherrer's formula. D _c = kλ / β · cos θ where β: half width (radian) θ: diffraction angle (°) k: 1 λ: X-ray wavelength (1.5418 °)

(14) Crystallinity X _c by Wide Angle X-ray Diffraction A wide angle X-ray diffraction intensity curve obtained by the same apparatus as that of (13) is separated into a crystal part and an amorphous part, and is obtained by the area method according to the following equation. Was. X _c = calculated as the product of the (crystalline part of the scattering intensity / General scattering intensity) × 100 (15) crystal phase birefringence [Delta] n _c the crystal orientation degree f _c and full crystal birefringence [Delta] n _cm (using 0.213) Was. Note that f _c wide angle X-ray diffraction by (010), those obtained by using the following equation (100) intensity distribution curve half-width H ° along the Debye ring of the equator interference. f _c = (180−H) / 180

(16) Processing cord performance Intermediate elongation KE: Elongation at the time of a stress of 6.75 kg of the processing cord. Utilization ratio for original yarn: The ratio of the treatment cord strength to the drawn yarn strength was shown as a percentage. Dimensional stability: Expressed as the sum of dry heat shrinkage HS at 150 ° C. and intermediate elongation KE. Utilization ratio for vulcanized fiber: The ratio of the post-vulcanization strength to the strength equivalent to two drawn yarns was expressed as a percentage. The vulcanization conditions were a temperature of 153 ° C., a pressure of 60 kg / cm ² , and a treatment time of 60 minutes. After vulcanization, the rubber cord was peeled off and the strength was measured. Fatigue strength utilization ratio against original yarn: The ratio of the strength of the cord after the fatigue test to the strength equivalent to two drawn yarns was shown as a percentage. The fatigue test was performed using the disk method JISL-1017-1693 (1.3.2.
The strength of the cord after a 72-hour fatigue test was measured. Tube heat generation temperature: In a tube fatigue test according to JISL-1017-1963 (1.3.2.1) Method A (Goodyear method), the rubber surface temperature after a 100 minute fatigue test was measured with a non-contact thermometer.

Examples 1 to 8 A polyethylene terephthalate chip having an intrinsic viscosity [η] of 0.55 to 0.75 was prepared by adjusting the terminal carboxylic acid concentration (COOH) to 8 to
Melt spinning was performed by a screw extruder while adding N, N'-bis (2,6 diisopropyl) phenylcarbodiimide so as to be in the range of 10 (eq / 10 ⁶ g). The polymer temperature at this time was 305 as shown in Tables 1 and 2.
° C or lower, and a spinneret having a hole diameter of 0.35 mm and concentrically arranged holes was used.

The spun yarn discharged from the spinneret has a length
After passing through a heating zone of 100mm, internal surface temperature 300 ℃,
Cooling and solidification was achieved by blowing cooling air at a temperature of 20 ° C and a relative humidity of 80% from the outer periphery of the thread. Next, an oil agent was applied with an oiling nozzle, and was once wound as an undrawn yarn at a spinning speed of 6.0 to 8.0 km / min.

Then, the obtained undrawn yarn is drawn at a take-up speed of 1500 m / min by a drawing machine including a take-up roller, a first draw roller, a second draw roller, a relax roller, and a take-up machine while being combined.・ Heat treatment was performed to obtain various deniers of 1500 denier / 255 filaments.

The working conditions according to the present invention and the physical properties of the undrawn yarn are shown in Examples Nos. 1 to 8 in Tables 1 and 2, and the physical properties of the drawn yarn are shown in Examples Nos. 1 to 4 in Tables 3, 4 and 5. 8 is shown. Here, the stretching ratio DR1 under the stretching and heat treatment conditions in Tables 1 and 2 is the ratio of the peripheral speed of each of the above-described take-up roller and the first stretching roller, and DR2 is the first stretching roller and the second stretching roller. The ratio of the peripheral speed of the roller, R
Is the ratio of the peripheral speeds of the second stretching roller and the relaxing roller. FR, 1GD, 2GD,
RR indicates a take-up roller, a first stretching roller, a second stretching roller, and a relaxation roller, respectively.

Further, the spinning state and the drawing state in Tables 1 and 2 are defined as the results obtained by objectively judging from the occurrence of fuzz during spinning / drawing, the state of thread breakage and the observation of the obtained fuzz. It is shown. The drawn polyester fiber yarns obtained in the above Examples 1 to 8 have a fine structure in which the uniformity (cross ratio) of the single fibers is excellent and the extremely high crystallinity and the relaxation of the distortion of the amorphous portion are remarkably advanced. , Melting point, strength, heat loss at the time of temperature rise such as work loss is extremely stable, and thermal dimensional stability such as heat shrinkage and thermal stress is remarkably improved,
The requirements of the present invention were satisfied in all aspects.

Comparative Example 1 Spinning, drawing and heat treatment were carried out under the same conditions as in Example 2 except that the spinning speed was 3.0 km / min and the draw ratio was 2.52 times. Tables 1 to 5 also show the conditions and physical properties. The obtained polyester fiber is crystalline (Tm1, Tm
2, Tm2 × ρ, X, D _c ), Δn, amorphous part parameter
(tan δ, Tmax), thermal characteristics at heating (ΔE, stability coefficient, Δ
TS / T), and does not satisfy the requirements of thermal dimensional characteristics (heat shrinkage, heat shrinkage stress).

Comparative Example 2 Spinning and drawing were performed in exactly the same manner as in Example 2 except that the spinning speed was 3.0 km / min, the polymer temperature was 310 ° C., the chip viscosity was 0.95, and the draw ratio was 2.35. Table 1 to Table 5
The conditions and physical properties are shown below. The obtained polyester fiber has poor single fiber uniformity (cross ratio) and strength ratio to intrinsic viscosity (TS / [η]), and has poor crystallinity (Tm1, Tm2, Tm).
2 × ρ, X, D _c ), Δn, amorphous part parameter (tan
δ, Tmax), thermal characteristics at heating (ΔE, stability coefficient, ΔTS /
T) does not satisfy various requirements for thermal dimensional characteristics (heat shrinkage, heat shrinkage stress).

Comparative Example 3 Spinning, drawing and heat treatment were carried out under the same conditions as in Example 2 except that the spinning speed was 4.5 km / min and the draw ratio was 1.68. Tables 1 to 5 also show the conditions and physical properties. The obtained polyester fiber is crystalline (Tm1, Tm2, Tm2
× ρ, X, D _c ), Δn, amorphous part parameters (tan δ,
Tmax), thermal characteristics at heating (ΔE, stability coefficient, ΔTS / T)
Does not satisfy the requirements for thermal dimensional characteristics (heat shrinkage, heat shrinkage stress).

Comparative Example 4 A chip viscosity of 0.95, a polymer temperature of 310 ° C., and a draw ratio of
Except for 1.19 times spinning and spinning under the same conditions as in Example 2.
Stretching and heat treatment were performed. Tables 1 to 5 also show the conditions and physical properties. At the time of spinning, single yarn fusion and yarn twisting occurred, and yarn breakage and fluff increased. In addition, yarn breakage and fluff occurred frequently in the stretching and heat treatment steps.

The obtained polyester fiber has a single fiber uniformity (cross ratio) and a strength ratio to the intrinsic viscosity (TS /
[Η]), crystallinity (Tm1, Tm2), amorphous parameters (tanδ, Tmax), thermal characteristics at heating (ΔE, stability coefficient, ΔTS / T), thermal dimensional characteristics (heat shrinkage, Heat shrinkage stress)
Does not meet the requirements of

Comparative Example 5 Spinning, stretching and heat treatment were carried out under exactly the same conditions as in Example 2 except that the draw ratio was set to 1.35 times, which was too large for the present invention. Yarn breakage and fluff occur frequently in the stretching and heat treatment steps, and the obtained polyester fiber has an elongation and E2 / E
Since the value of 1 is too small, it is not preferable because the utilization factor for the raw yarn for the following processing code is remarkably deteriorated and the strength is lowered.

Comparative Example 6 Spinning, stretching and heat treatment were carried out under exactly the same conditions as in Example 2 except that the stretching ratio was set to 1.19 times, which was too small for the present invention. The obtained polyester fiber is not preferred because E2 / E1 is too large, and the strength when the following treatment cord is used is low, and the vulcanization power utilization rate is low.

Comparative Example 7 A chip viscosity of 0.40, a polymer temperature of 290 ° C., and a draw ratio of
Except for 1.24 times spinning and spinning under the same conditions as in Example 2.
Stretching and heat treatment were performed. Thread breakage during stretching / heat treatment process,
The obtained polyester fiber is unfavorable because the fluff frequently occurs and the obtained polyester fiber has low T1 and strength TS.

Examples 11 to 18 and Comparative Examples 11 to 17 The drawn yarns obtained in the above Examples and Comparative Examples were twisted by a twisting machine at 400 T / m in the Z direction and 400 T / m in the S direction.
After applying an adhesive containing resorcinol / formalin / rubber latex as a main component to the twisted cord, the thread is heated at 160 ° C. under dry heat and at a constant length for 90 seconds, and at 240 ° C. under dry heat tension for 120 seconds. A heat treatment was performed for 40 seconds at 240 ° C. in a dry heat / relaxed state to obtain a treatment code. The tension rate and relaxation rate were set in accordance with the physical properties of the drawn yarn so that the elongation of the treated cord under a stress of 6.75 kg was 3.5 to 4.0%.

Table 6 shows the processing code performance in the above Examples 11 to 18 and Comparative Examples 11 to 17. The treatment codes shown in Examples 11 to 18 and Comparative Examples 11 to 17 are manufactured using drawn yarns of Examples and Comparative Examples obtained by subtracting 10 from the numbers of Examples and Comparative Examples. Examples 11 to 18 have high strength at elevated temperature, low tube heat generation temperature and high fatigue resistance,
It exhibits characteristic effects such as low heat shrinkage and excellent dimensional stability, and exhibits excellent thermal dimensional stability.

On the other hand, in Comparative Examples 11 to 13, the strength at the time of raising the temperature was low and the tube heat generation temperature, fatigue resistance, heat shrinkage, and thermal dimensional stability were insufficient. In Comparative Example 14, the cord strength was low, and the strength at the time of temperature rise, tube heat generation temperature, fatigue resistance, heat shrinkage, and thermal dimensional stability were insufficient. Comparative Example 15 has a low utilization rate of the yarn resistance and a low cord strength. Comparative Example 16 is inferior in cord strength and utilization rate of vulcanization to raw yarn. Comparative Example 17 is not preferable because the utilization rate of the original yarn is low and the cord strength is low.

[0088]

[Table 1]

[Table 2]

[Table 3]

[Table 4]

[Table 5]

[Table 6]

[0089]

The polyester fiber of the present invention has extremely high crystallinity and remarkably progresses the relaxation of the distortion of the amorphous part as unprecedented, so that the thermal characteristics such as melting point, strength, work loss and the like are increased. It is extremely stable at the time of warming and has significantly improved thermal dimensional characteristics such as heat shrinkage and heat shrinkage stress. That is, when the polyester fiber of the present invention is used as a fiber for reinforcing a rubber structure, a decrease in strength and a decrease in expected modulus at the time of temperature rise are small, work loss is small and heat generation due to this is small, Low creep rate of
It exhibits characteristic effects such as a small heat shrinkage ratio, and exhibits excellent thermal properties at elevated temperatures comparable to rayon fibers and excellent thermal dimensional stability comparable to rayon.

[Brief description of the drawings]

FIG. 1 shows the peak value of the mechanical loss tangent of a polyester fiber.
The figure which shows the relationship between tandelta and peak temperature Tmax. The range A is the polyester fiber of the present invention, B is the polyester fiber obtained by the conventional "POY-drawing method", and C is the undrawn system according to the present invention.

FIG. 2 is a view showing a stress-elongation curve of a polyester fiber.
“a” is a polyester fiber according to the present invention, and “b” is a polyester fiber obtained by a conventional “POY-drawing method”.

FIG. 3 is a diagram showing the relationship between the dry heat shrinkage of polyester fibers and the degree of stability. D is a polyester fiber according to the present invention,
F is a polyester fiber obtained by the conventional "POY-drawing method".

FIG. 4 is a diagram showing a change in strength of a polyester fiber depending on a heating temperature. G is a polyester fiber according to the present invention, and H is a polyester fiber obtained by a conventional “POY-drawing method”.

FIG. 5 is a diagram showing a relationship between a heating temperature and a shrinkage ratio of polyester fibers. I is a polyester fiber according to the present invention, and J is a polyester fiber obtained by a conventional "POY-drawing method".

FIG. 6 is a view showing a heat shrinkage stress curve of a polyester fiber.
c is a polyester fiber according to the present invention, and d is a polyester fiber obtained by a conventional “POY-drawing method”.

FIG. 7 is a diagram showing the relationship between the spinning speed of polyester fiber and the birefringence. A polyester fiber having a range K according to the present invention;
L is a polyester fiber obtained by the conventional “POY-drawing method”.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-57-154410 (JP, A) JP-A-53-58031 (JP, A) JP-A-62-69819 (JP, A)

Claims (2)

(57) [Claims] 1. A ethylene terephthalate as a main recurring unit, a polyester fiber characterized in that it comprises the following properties simultaneously, (a) intrinsic viscosity [η] = 0.5 0 ~0.75 (b) Mechanical loss peak tangent (tan [delta) and peak temperature (Tmax) tanδ ≦ 0.140 Tmax ≦ 130 ℃ (c) of the elongation E ₂ up to the cutting point after secondary yield point for elongation E ₁ in the secondary yield point Elongation ratio E ₂ / E ₁ = 0.20 to 0.49 (d) Stability indicated by the reciprocal of the product of 150 ° C. work loss ΔE and 175 ° C. dry heat shrinkage HS (but not more than 2.2%) (E) Ratio of strength TS to intrinsic viscosity [η] TS / [η] ≧ 9.2 (f) Heat shrinkage stress up to 200 ° C. is 0.2 g / d or less,
The peak of the heat shrinkage stress is 255 ° C or more, and the heat
Shrinkage stress is 0.10 g / d or less . 2. A method for producing a polyester fiber containing ethiten terephthalate as a main repeating unit. Melt spinning a polyester chip having an intrinsic viscosity of 0.50 to 0.80 at a spinning speed of at least 6.0 km / min; When the undrawn yarn is hot drawn, the draw ratio DR
And the hot stretching temperature DT is satisfied so as to satisfy the following (1) to (3), and DR = 1.20 to 1.30. . (1) (Tg-10) ≦ DT ₁ ≦ (Tg + 100). . (2) (Tg + 100) ≦ DT ₂ ≦ Tm ₂ . . (3) (where DT ₁ is the drawing temperature in the _{first half} of drawing, DT ₂ is the drawing temperature in the _{second half} of drawing, Tg is the glass transition point of fiber and Tm ₂
Indicates the crystal melting point of the fiber . ) , C. A method for producing a polyester fiber, comprising performing a relaxation heat treatment after the drawing.